Thailand has resolved to unilaterally cancel the 2001 maritime MoU with Cambodia, moving forward with international mechanisms to address the maritime disputes. Cambodia swiftly responded, reaffirming its commitment to pursue “compulsory conciliation” under the United Nations Convention on the Law of the Sea (UNCLOS).

At its meeting on Tuesday (5 May), the Thai cabinet resolved to cancel the 2001 Memorandum of Understanding on the maritime areas claimed by both Cambodia and Thailand, which has served as a framework for resolving maritime boundary disputes in the Gulf of Thailand between the two countries.

Thai Prime Minister Anutin Charnvirakul revealed that Thailand is preparing to formally inform Cambodia of the cancellation, adding that the decision was not related to the conflict with Cambodia.

He said the agreement had made no significant progress during the past 25 years. The PM told the media that from now on ‘the 2001 MoU’ will no longer exist for Thailand, and that any future negotiations would be carried out under new conditions.

Thai Foreign Minister Sihasak Phuangketkeow also asserted that cancelling the agreement did not mean that Thailand was ruling out further negotiations with Cambodia, noting that Thailand will pursue negotiations through an international framework, particularly under UNCLOS.

Both Thailand and Cambodia are currently parties to UNCLOS, with the latter recently ratifying the Convention in January. However, in 2011, Thailand issued a formal declaration under Article 298 that it does not accept compulsory jurisdiction of international courts in certain issues, including ‘maritime boundaries delimitation’. 

However, alternative mechanisms under UNCLOS could still be applied to Thailand.

According to the 2001 MoU, Thailand and Cambodia have an overlapping claims area of 26,000 square kilometres. Around 10,000 square kilometres north of latitude 11° North is still to be delimited, while the remaining area was designated as a Joint Development Area (JDA) for joint energy exploration and drilling.

The agreement established a two-track framework, requiring that both JDA and delimitation must be negotiated ‘in parallel’.

Cambodia proclaimed its continental shelf in 1972 and based its claim on its interpretation of the 1907 Franco-Siamese Treaty, while Thailand proclaimed its own in 1973, relying on the 1958 Geneva Conventions on the Law of the Sea.

Thailand argued that Cambodia cannot apply the treaty given that the 1907 Treaty was intended solely to define land boundaries, not maritime ones. Notably, the concept of maritime boundaries had not yet been established in international law at the time.

Amid rising nationalist sentiment linked to the conflict with Cambodia, several Thai nationalist groups have called on the government to unilaterally cancel the 2001 MoU on the grounds that the agreement could lead to the loss of territory, particularly Ko Kut.

The proposal to cancel the 2001 MoU was also a part of the ruling Bhumjaithai Party’s election campaign, reflecting Anutin’s tough stance towards Cambodia, which resonated with patriotic voters and helped consolidate support for the Party in the last election.

It later appeared in the policy statement delivered to parliament on 9 April, which stated that the government will expedite a study on the possible cancellation of the 2001 MoU.

“It is regretful that Thailand has decided to unilaterally withdraw from this Memorandum of Understanding. For Cambodia, we have always given priority to bilateral mechanisms in line with this Memorandum of Understanding for dealing with our overlapping maritime area,” stated Cambodian PM Hun Manet in response to Thailand’s unilateral cancellation.

He said Cambodia would be left with no choice but to rely upon international law, including UNCLOS, particularly the ‘Compulsory Conciliation’ mechanism under this Convention.

“Therefore, Cambodia’s decision reflects our sincere hope that both countries can reach a just and lasting solution in line with international law, allowing our peoples to live together in peace, stability, and harmony,” added the Cambodian PM.

Cambodia's Foreign Minister Prak Sokhonn also expressed regret over Thailand's decision to cancel the MoU, which had served as a cooperative mechanism and a reflection of mutual political will for both sides to resolve maritime disputes.

If Cambodia unilaterally pursues compulsory conciliation, Thailand will be left with no choice, given that the mechanism requires compulsory attendance for all parties involved, according to Article 11 of Annex V.