World June 2, 2026 11:22 PM

Cambodia Invokes Little-Used UN Procedure to Press Maritime Claim Against Thailand

Phnom Penh initiates compulsory conciliation under UNCLOS over a disputed 26,000 sq km Gulf of Thailand zone rich in hydrocarbons

By Sofia Navarro

Cambodia has opened a compulsory conciliation procedure under the United Nations Convention on the Law of the Sea (UNCLOS) to address a long-standing maritime boundary contest with Thailand. The disputed area, roughly 26,000 square kilometres in the Gulf of Thailand, is estimated to contain about 12 trillion cubic feet of natural gas and substantial oil reserves valued at around $300 billion. The process yields non-binding recommendations from a Conciliation Commission and mirrors a mechanism previously used by East Timor in talks with Australia.

Cambodia Invokes Little-Used UN Procedure to Press Maritime Claim Against Thailand

Key Points

  • Cambodia has invoked compulsory conciliation under UNCLOS to address a maritime boundary dispute with Thailand over about 26,000 sq km in the Gulf of Thailand.
  • The disputed area is estimated to contain nearly 12 trillion cubic feet of natural gas and oil resources valued at about $300 billion, affecting the energy sector and regional resource development.
  • The conciliation mechanism produces non-binding recommendations from a five-member Conciliation Commission and has been used successfully in the past by East Timor in talks with Australia.

Cambodia has formally launched a rarely used United Nations arbitration route known as compulsory conciliation to seek resolution of a decades-long maritime boundary dispute with Thailand and to gain access to what it says are significant oil and gas deposits in the contested waters.

The two neighbours have for more than 25 years claimed overlapping rights to an area of about 26,000 square kilometres in the Gulf of Thailand. Estimates cited by Cambodian authorities put the contested maritime belt at nearly 12 trillion cubic feet of natural gas and substantial quantities of oil, with a combined value of approximately $300 billion.

In 2001 the countries agreed to a framework intended to permit joint development of the energy resources in the so-called "overlapping claims area." That arrangement, however, was unilaterally ended by Thailand last month, a move that fulfilled an election promise by Thai Prime Minister Anutin Charnvirakul and followed two rounds of deadly clashes along a disputed land frontier last year.


What compulsory conciliation entails

On Tuesday, Cambodia said it had initiated compulsory conciliation under UNCLOS. The procedure allows any state party to the convention to commence proceedings against another party. Under the mechanism each state appoints two conciliators to form a panel called the Conciliation Commission, which then selects a fifth member to serve as chair.

The role of the commission is to investigate the facts and the legal positions of the parties and to produce a set of recommendations. Those recommendations are non-binding. The commission also prepares a report of its findings and forwards that document to the United Nations secretary-general.


Past use of the mechanism

The compulsory conciliation route has seen limited application. To date, the most notable use was by East Timor - also known as Timor Leste - in its maritime dispute with Australia. East Timor initiated the process on April 11, 2016 when it issued a notice to Australia; Australia agreed to participate only weeks later. Less than two years of negotiations followed, and in early March 2018 the two countries signed a maritime boundary treaty at United Nations headquarters in the presence of the UN chief.


Next steps and appointments

Cambodia has designated its foreign minister, Prak Sokhonn, to act as its agent in the proceedings. Phnom Penh has also named two conciliators: Danish diplomat Peter Takse-Jensen and French academic Jean-Marc Thouvenin. Takse-Jensen previously chaired the commission that negotiated between East Timor and Australia.

Thailand has a 21-day window, beginning when it receives the formal notice, to appoint its two conciliators. If Thailand does not meet that deadline, Cambodia may ask the UN secretary-general to appoint those members on Bangkoks behalf, according to a statement from the Cambodian government.

Thai Prime Minister Anutin said on Tuesday that he was not aware Cambodia had launched the compulsory conciliation process, and added that his government would utilise UNCLOS principles in its next actions. He also said Thailand had not yet determined when it would proceed further.

Once four members of the commission are in place, those members are to select a chairperson within 30 days, after which the commission will begin further proceedings.


Implications

The move marks a formal escalation in legal terms by Cambodia to seek international examination of the competing claims. The procedure offers a structured path to clarifying both factual and legal questions, but its recommendations do not carry binding force. The timetable and ultimate outcome will depend on Thailands engagement with the process and on how the commission frames its findings and proposals to the UN secretary-general.

Risks

  • Thailand has recently terminated the 2001 joint development pact and has not yet appointed conciliators, creating timing uncertainty for the process - this affects timelines for energy exploration and investment.
  • The Conciliation Commission issues non-binding recommendations, meaning any resolution does not guarantee enforceable access to the contested hydrocarbon resources - this raises commercial and legal risk for energy and infrastructure stakeholders.
  • The outcome depends on Thailands level of participation and on the commissions eventual recommendations, leaving market participants uncertain about the pace and scope of any resource development in the disputed area.

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