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10 July 2019 – 19 June 2025 Anutin Acting Prime Minister

Should MOU 44 be revoked when the resolution of maritime disputes under UNCLOS cannot be predicted 100%?

Prachatai / Special Report / Politics / Economy / Foreign Affairs / Security

Published on March 4, 2026.

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ការឃោសនាមុនការបោះឆ្នោត ដើម្បីលុប MOU43, 44 និងការឈ្នះឆ្នោត

ការឃោសនាមុនការបោះឆ្នោត ដើម្បីលុប MOU43, 44 និងការឈ្នះឆ្នោត

Report by: Natthaphol Mekhsophon

Following the general election on February 8, 2026, in Thai politics, it is becoming clearer that the Bhumjaithai Party won the election and will lead the formation of the new government. This means that the policies promised to the public during the election campaign are likely to proceed, including the cancellation of Memorandums of Understanding (MOUs) 43 and 44.

Shortly after the election, just two days later, Prime Minister Anutin Charnvirakul told the media that he would instruct the Ministry of Foreign Affairs and the Ministry of Defence to form a working group to study the cancellation of the memorandum of understanding between Thailand and Cambodia regarding overlapping continental shelf claims, also known as MOU 44.

Anutin Charnvirakul (Source: Thai Khu Fah Facebook page )

For those unfamiliar with MOU44, this memorandum of understanding is a treaty signed between Thailand and Cambodia during the Thaksin Shinawatra government in 2001. Its primary purpose was to provide a framework for negotiations between Thailand and Cambodia regarding overlapping maritime boundary claims covering an area of ​​26,000 square kilometers, divided into two main areas:

An area north of 11 degrees north latitude, covering 10,000 square kilometers, is the overlapping maritime boundary that Thailand and Cambodia will need to negotiate.

In the area south of latitude 11 degrees north, covering an area of ​​16,000 square kilometers, Thailand and Cambodia will need to negotiate the joint exploitation of subterranean natural resources, such as petroleum, natural gas, and others, without the need to divide maritime territories.

In addition to the issue of overlapping maritime claims, MOU 44 also stipulates that Thailand and Cambodia must agree on maritime boundary demarcation and the development of their respective petroleum industries simultaneously. Furthermore, both countries must negotiate and reach an agreement as quickly as possible.

For those interested in reading more about MOU44, please click on this link.

Understanding MOU 44: A Simple and Comprehensive Explanation of Reasons for Cancellation vs. Non-Cancellation

However, the context for negotiating maritime boundary disputes may change significantly because on January 16, 2026, less than a month before Thailand's parliamentary elections, the Cambodian government announced its ratification of the United Nations Convention on the Law of the Sea (UNCLOS), which will come into force in March 2026.

How will Cambodia's ratification of the MOU impact negotiations between Thailand and Cambodia on the overlapping maritime claims? Join us in finding the answers with Professor Patarapong Saengkrai from the Faculty of Law, Thammasat University, on various issues related to MOU 44 and the dispute settlement mechanism under the UNCLOS Convention, and how it affects signatory countries.

Can MOU44 be unilaterally revoked?

Previously, there was a debate about whether, since MOU 44 between Thailand and Cambodia has the status of a treaty under the Vienna Convention, it can be unilaterally revoked with the consent of both parties, or unless one party seriously violates the agreement. The question, in reality, is whether MOU 44 can be unilaterally revoked.

Professor Phatarapong stated that, according to treaty law, one must first examine the treaty's contents regarding the cancellation of the agreement. If it is explicitly stated, then it must be followed. However, if it is not specified in the treaty, the general principle applies: both parties must 'agree to cancel the agreement.'

However, Professor Phatarapong explained that the principle of mutual consent has an exception allowing for unilateral cancellation, depending on whether the content of the treaty allows for unilateral cancellation, as per Article 56(1)(b) of the Vienna Convention of 1969.

Professor Phatarapong believes that the party seeking to cancel the agreement would argue that the content of MOU44 allows Thailand to unilaterally revoke it. This is because MOU44 is not a final, definitive agreement, but merely an ' Agreement to Negotiate, ' meaning both parties agree to "negotiate" within the framework specified in the treaty.

"(MOU44) only stipulates that the two parties must negotiate, and it doesn't guarantee that the negotiations will lead to a genuine (maritime) boundary demarcation. Essentially, it's their duty to negotiate, and they must expedite the negotiations to reach a conclusion, because at that time, there was only a shared political will from both sides; it hadn't yet reached the point of demarcation or sharing of benefits. This means that, in essence, if the negotiations are inconclusive, the agreement can be unilaterally canceled. The content of MOU44 doesn't create very strict provisions," Patarapong said, adding that if it were canceled, the mechanism for resolving future disputes would be under the framework of the UNCLOS convention.

The map showing the claimed maritime boundaries in the overlapping area, attached to MOU 44 (Source: Report " Should the Memorandum of Understanding of 2001 (MOU 2001) concerning the maritime boundary between Thailand and Cambodia be terminated? " by the Foreign Affairs Committee of the Senate), with Prachatai emphasizing the lines even more clearly.

The outcome of dispute resolution under UNCLOS is unpredictable.

Legal experts view Cambodia's ratification of the UNCLOS convention, which will officially enter into force on March 8, 2026, as a significant shift in its bargaining power.

Professor Phatarapong further stated that UNCLOS dispute settlement will end when two countries can negotiate together. However, if negotiations fail, the party state has the right to use the dispute settlement mechanism, which has three forms:

International arbitration

The International Tribunal for the Law of the Sea (ITLOS)

International Court of Justice (ICJ)

A professor from Thammasat University further explained that if Thailand and Cambodia cannot agree on which court to use to resolve the case, they would have to resort to arbitration. However, if they are hesitant to go to arbitration for various reasons, such as high costs, they may choose the compulsory dispute resolution mechanism , or "Compulsory Conciliation." This involves appointing qualified experts as neutral parties to listen to both sides' perspectives and propose concrete solutions. If Thailand is confident that its legal claims and evidence are strong, and that Cambodia has incorrectly drawn the maritime boundary, then Thailand should win the arbitration case. However, there are two problems: 1. What constitutes a "winning" decision? This involves strategizing the case, and 2. No one can predict the outcome with 100% certainty.

"Because the relevant legal principle under UNCLOS only states 'an equitable solution,' which is not the same as drawing a straight line to divide things 50-50. Drawing a straight line isn't always 'fair.' 'Fairness' doesn't mean ' equality .' One problem is that when we proceed to court or arbitration, it's ' unpredictable' that we can't entirely predict the outcome of the decision," Patarapong said.

Professor Phatarapong emphasized that " the principle of achieving fairness" is not the same as "the principle of equality." These two are different because Cambodia's argument is that it is a small, developing country with limited access to the sea from Vietnam, while Thailand is more developed. It's possible that if the decision is based on this principle, Cambodia might benefit more. However, if both countries negotiate and reach an agreement beforehand, both sides will consider the outcome of the negotiations to be " fair. " If they cannot agree, a mediator might be brought in to determine a fair division of the spoils.

Reservation 298 exempts the case from the International Court of Justice, but disputes must still be resolved according to UNCLOS.

When asked whether Thailand's reservation under Article 298 of the UNCLOS would exempt it from the International Court of Justice or arbitration, Professor Patarapong confirmed that yes, but only on matters of maritime boundary delimitation, military activities, and actions taken in accordance with UNSC resolutions. He explained that the UNCLOS convention grants rights to states in these areas because they are sensitive issues for many countries, and the parties involved prefer to negotiate amongst themselves.

However, even if we do not use the UNCLOS maritime boundary dispute settlement system, the Convention framework will still require the states involved to settle the dispute together, as per Article 298(1), as has happened with Timor-Leste and Australia.

Pattarapong revealed that Timor-Leste and Australia have had a dispute in the Timor Sea (since 2002), which can be compared to Thailand's case. At that time, when Australia saw that Timor-Leste was about to become a party to the UNCLOS convention, Australia preemptively declared that it would not recognize the jurisdiction of the courts and arbitrators in matters relating to maritime boundary demarcation.

Later, when Timor-Leste became a party to UNCLOS, it could not seek arbitration on this matter. However, under the UNCLOS convention, "Compulsory Conciliation" (as per Annex 5, Article 2) was established. Ultimately, Timor-Leste and Australia were able to resolve the dispute under this compulsory conciliation process because the dispute was protracted and could not proceed further. Timor-Leste and Australia agreed to develop and share the benefits, with Timor-Leste receiving 90% of the benefits and Australia receiving 10%.

Is Cambodia preparing to negotiate within the UNCLOS framework?

Regarding the media's question about the future direction of dispute resolution, Professor Patarapong believes that considering Prime Minister Anutin's repeated emphasis on revoking MOU 44 before, during, and after the election, and the subsequent establishment of a working group, it seems the Prime Minister is likely instructing that negotiations not be further delayed. Something must be done, which might involve revoking or amending MOU 44.

Meanwhile, looking ahead to Cambodia, if they perceive that the MOU 44 negotiations are not progressing, Cambodia might propose using the arbitration mechanism under UNCLOS to resolve the dispute. If Thailand rejects this, then compulsory conciliation would be necessary. Therefore, Cambodia should prepare itself in parallel, both for negotiations with Thailand within the framework of MOU 44 and for the possibility of using the "Compulsory Conciliation" mechanism. Thailand should also prepare itself in terms of these mechanisms, and the government should ensure that its citizens understand this process.

Cambodia is conducting overseas trips as part of preparation for a potential territorial dispute.

Regarding the media's question about whether Cambodian Prime Minister Hun Manet's recent meetings with various world leaders are in preparation for the border dispute with Thailand, Professor Patarapong believes that, judging from Hun Manet's interviews, the focus remains on the land border, MOU 43, or the JBC (Thai-Cambodian Joint Border Commission). This is understandable, as the Cambodian people are partly pressuring him and partly waiting to see how the situation will unfold. Therefore, his meetings with the media and world leaders are a way to address the concerns of his domestic citizens. On the other hand, it also puts pressure on Thailand, because Cambodia has consistently argued that the area occupied by Thai troops (following the latest clashes) encroaches on Cambodian territory, exceeding Thailand's claimed sovereignty. Thus, Cambodia's meetings with the media and foreign leaders may not yet include maritime issues.

(Left) Hugh Manet and (Right) Emmanuel Macron (File photo taken on February 5, 2024 at the Présidence de la République France ).

However, law professors believe that asking France for assistance with evidence may involve maritime issues.

"What is being viewed and is a concern, and is also included in Senator Prachit 's study, is the definition of the territorial sea. The line that Cambodia claims extends from kilometer marker 73 to the center of Koh Kood, citing treaties. Many on the Thai side insist that this claim is invalid because the treaties of 1904 and 1907 concerned land boundaries, but Cambodia is trying to apply them to the sea. The straight line drawn from Koh Kood and curving southward is what they claim based on the treaties. Therefore, if they can provide evidence that it can be applied to the territorial sea, then they can make their claim. But the Thai side has consistently maintained that such a claim is not valid," Patarapong stated.

A research report titled "Should the Memorandum of Understanding of 2001 (MOU 2001) Concerning the Maritime Boundary between Thailand and Cambodia be Termination?", written by Prachit Rojnapruk, former Senator and former Director-General of the Department of Treaties and Law, Ministry of Foreign Affairs, states on page 3, under the heading " Ownership of Koh Kood," that Cambodia has declared a continental shelf line, using a straight line dotted as shown in the annex to the 1907 treaty between Siam and France, as the dividing line for the "continental shelf" and the "territorial sea" between Thailand and Cambodia.

On this point, the Thai side argues that the 1907 treaty does not delineate a maritime boundary; it only defines a land boundary, and the symbol +++, used for demarcation of the maritime boundary, does not appear.

Should MOU44 be revoked?

Regarding the issue of whether MOU 44 should be revoked, Professor Patarapong commented that revocation is only one aspect of the larger problem. Even if Thailand doesn't revoke it and continues negotiations within the framework of MOU 44, there is currently a lack of trust in the negotiation process within that framework, as well as distrust of government officials, including the Hydrographic Department of the Ministry of Foreign Affairs and politicians. This puts increased pressure on the negotiating team. Achieving a resolution with Cambodia is already difficult, but negotiating a result that satisfies the Thai people is even more challenging. Otherwise, it could face opposition similar to the Preah Vihear Temple case. If MOU 44 is revoked, the question arises: what mechanisms will be used? If the UNCLOS mechanism is applied, how can the public, who have lost trust in the MOU, regain trust in the government and its officials?

Pattarapong continued, "This situation makes us realize that whether we negotiate within the framework of MOU 44 or a new replacement, as long as a number of people don't trust the officials negotiating, combined with the societal sentiment following last year's clashes (in 2025), which has increased hatred towards Cambodia, it's unclear how we will reach an agreement. Many people are even saying that the line Thailand claims is unacceptable if it's not 100% valid. In reality, that's impossible. There has to be a compromise; one side must concede on one point, and the other must concede on another. Flexibility is necessary. Therefore, maintaining the old framework or replacing it with a new one makes negotiations difficult, and it might end up in dispute resolution under UNCLOS, involving a third party. The remaining issue is communicating with our people that, 'If we want this dispute to be definitively resolved so we can use the oil and natural gas, then we should accept the advice or rulings from a third party.'"

“There are two main objectives: firstly, to negotiate with Cambodia, and secondly, to communicate and convince the entire country. I’d like to add that some have suggested that the negotiating team should include representatives who oppose MOU 44, to participate in the decision-making process. It’s about managing mistrust,” Patarapong said.