The Thai cabinet voted on 5 May 2026 to terminate the 2001 Memorandum of Understanding with Cambodia on overlapping maritime claims. Within hours, Cambodian Deputy Prime Minister and Foreign Minister Prak Sokhonn announced that Cambodia would initiate compulsory conciliation under the United Nations Convention on the Law of the Sea.
Both moves were prepared.
Cambodia ratified UNCLOS on 6 February 2026, three months before the Thai cabinet decision. The Convention entered into force for Cambodia on 8 March 2026. The instrument of ratification carried a declaration under Article 298 excluding all three categories of disputes referred to in subparagraphs 1(a), (b), and (c) of that article. Thailand’s own Article 298 declaration filed in 2011 excludes the same three categories. The two declarations are mirror images. Each state made the same exclusion on the same subparagraphs, which forecloses any reciprocity-based challenge by either to the scope of the other’s declaration.
That symmetry is the point of the architecture now in motion.
UNCLOS Article 281 makes Part XV dispute settlement procedures available only where a bilateral mechanism has not produced settlement and the agreement does not exclude further procedure. While MOU 2001 remained in force as the bilateral framework for the overlapping maritime claims, Article 281 routed any UNCLOS proceeding back to the bilateral track. MOU 2001 contains no clause excluding further procedure, so the Article 281 shield was structurally weaker than the second one. Article 298(1)(a)(iii) added that second shield, barring the Annex V conciliation pathway for any sea boundary dispute “to be settled in accordance with a bilateral or multilateral agreement binding upon those parties.” MOU 2001 served as that bilateral agreement.
Cancellation removes both shields at once.
What remains is the proviso embedded in Article 298(1)(a)(i) itself. Both states’ declarations invoke the article that contains it. The proviso states that any party that filed the exclusion must still accept compulsory conciliation under Annex V Section 2 if the dispute arose after Convention entry into force, does not necessarily involve concurrent consideration of land-territory sovereignty, and has not been settled in negotiations within a reasonable period. Three gates. Cleared, the procedure becomes mandatory on the other party’s request. The commission produced under Annex V Section 2 issues a report; the report is not binding. The procedural fight that produces it is.
The temporal gate is the one Cambodia has to clear on its own side. UNCLOS entered into force for Cambodia on 8 March 2026. The overlapping maritime claims predate that. Whether the dispute Cambodia invokes “arose subsequent” to entry into force on Cambodia’s side, when the underlying claims trace to the 1970s and the active diplomatic phase to the conflict cycle of 2025, is the question Thailand has the strongest opening to litigate. Cambodia’s drafting of the dispute will have to clear that gate before the substantive architecture matters.
This is what Sokhonn invoked.
His statement, delivered at a press conference at the Ministry of Foreign Affairs and International Cooperation in Phnom Penh, said that following Thailand’s withdrawal Cambodia had no option but to turn to UNCLOS mechanisms, particularly compulsory conciliation, to resolve the dispute peacefully and under international law. The Phnom Penh Post quoted Sokhonn directly: “Today, following Thailand’s unilateral rejection of MoU-2001, Cambodia announces that it will initiate compulsory conciliation with Thailand under the UN Convention on the Law of the Sea.”
The pathway was named publicly before the cabinet vote. On 1 May, Sokhonn told Cambodian state broadcaster TVK that Cambodia would pursue peaceful, law-based solutions if Thailand withdrew from MOU 2001. Secretary of State Kung Phoak made the same point publicly between 1 and 3 May. The procedural pathway was named four days before the cabinet decision that triggered it.
Thai Prime Minister Anutin Charnvirakul cast the cancellation as overdue. “Cancelling the deal is not related to the border conflict with Cambodia, but part of my policy. It has been 25 years and there has been no progress,” he told reporters in Bangkok. His Bhumjaithai Party included MOU 44 termination as an election pledge in 2026. Anutin became the first Thai premier reelected in two decades, on a campaign Reuters described as riding “a wave of nationalism stoked by the fierce fighting with Cambodia.”
The same Reuters article that carried Anutin’s framing also named the documented stalling factors: “political instability in Thailand, intermittent disputes between the two neighbours and fierce opposition from Thai nationalists.”
Sixteen months earlier, Vice Minister for Foreign Affairs Russ Jalichandra had told Thailand’s Government Public Relations Department that MOU 44 was Thailand’s most effective tool for managing the maritime dispute. The statement also said cancellation would not eliminate Cambodia’s territorial claims. The 2009 Thai cabinet under Abhisit Vejjajiva voted to cancel the same instrument. The Yingluck Shinawatra government reversed that decision in 2014 after a review concluded the MOU could not be effectively replaced. The cycle, on the Thai institutional record, has now run twice.
The cabinet decision on 5 May is not yet legally complete. The Associated Press, citing Thai officials, reported that termination does not take legal effect until Thailand sends a formal notification letter to Cambodia. Pattaya Mail, citing the Thai Ministry of Foreign Affairs Department of Treaties and Legal Affairs, confirmed the same procedural sequence: the Department prepared the proposal, the National Security Council approved it, the cabinet ratified the approval on 5 May, and the formal notification letter is pending. Under the Vienna Convention on the Law of Treaties, which both states treat as customary international law, Article 56(1) provides that a treaty without a termination clause is not subject to denunciation or withdrawal unless the parties intended to admit that possibility or the right is implied by the nature of the treaty. Where withdrawal is permitted under that test, Article 56(2) requires twelve months’ notice. MOU 2001 has no termination clause. Articles 65 and 67 together require written notification specifying the measure proposed and the reasons, a three-month objection period, and a signed instrument from a head of state, head of government, or foreign minister.
None of that has happened.
What MOU 2001 also does not have is a dispute resolution clause. Its absence is what kept Article 281’s first prong intact while leaving the second prong, the requirement that the bilateral agreement “not exclude any further procedure,” structurally open. The text contains five operative articles and a signature block. Article 1 expresses the parties’ intent to “enter into provisional arrangements of a practical nature,” language that mirrors UNCLOS Articles 74(3) and 83(3). Article 2 commits the parties to negotiate joint development of hydrocarbon resources and maritime delimitation simultaneously, with a clause between Articles 2 and 3 stating their intent to treat both as “an indivisible package.” Article 5 preserves each party’s maritime claims until delimitation enters into force.
The framework was designed to be unsplittable: severing one track does not stall the other, it dismantles both at once.
Government spokesperson Rachada Dhanadirek told reporters the cancellation is “an adjustment of the framework for cooperation, not a termination of relations or negotiations.” Rachada also said UNCLOS would be used as a reference to negotiate directly with Cambodia on maritime boundary demarcation. Sokhonn invoked compulsory conciliation under Annex V Section 2.
They were proposing different procedures inside the same convention. Bilateral negotiation referenced to UNCLOS principles does not require Thailand’s consent to a forum it has not chosen. Compulsory conciliation under Annex V Section 2 does not require it either, once the three gates clear.
The Permanent Court of Arbitration registered the only prior compulsory conciliation under Article 298 and Annex V in 2016: Timor-Leste against Australia, on maritime boundary delimitation in the Timor Sea. Australia objected on competence; the conciliation commission ruled it was competent; the proceedings concluded in May 2018 with a signed treaty between the parties. The commission’s report was not binding. The treaty that followed it was.
Sokhonn said Cambodia will initiate. As of 5 May, the formal Annex V notification has not been filed with the Permanent Court of Arbitration’s Secretary-General. Cambodia announced intent. Thailand has approved a proposal. Neither state has executed the instrument that converts decision into legal effect.
Cambodian Prime Minister Hun Manet wrote on social media on 5 May that Cambodia’s decision reflects “our sincere hope that both countries can reach a just and lasting solution in line with international law.” The 2025 conflict killed close to 150 people across two rounds of fighting and displaced hundreds of thousands. The 817-kilometre border remains militarized at multiple points. The Joint Technical Committee created by MOU 2001 met in five rounds over two decades, according to AP, and never produced a delimitation agreement.
Thailand’s foreign ministry called MOU 2001 its most effective tool sixteen months before the cabinet voted to cancel it. The architecture that replaces it was ratified by Cambodia in February and made public by Cambodia four days before the vote.