PHNOM PENH: Cambodia is casting the UN Convention on the Law of the Sea (Unclos) as a critical legal safeguard for its maritime rights, as uncertainty grows over the future of bilateral mechanisms with Thailand governing overlapping sea claims.
The move follows the kingdom’s formal ratification of the convention by the National Assembly on Jan 16, 2026, with accession taking effect on March 8, making Cambodia the 172nd State Party to what is widely regarded as the “constitution of the ocean”.
Minister of information Neth Pheaktra explained that Unclos provides a “comprehensive legal basis” for managing maritime affairs, covering everything from navigation and fisheries to seabed resources and environmental protection.
“Unclos is the primary international legal instrument that sets out in detail and comprehensively the rules of the law of the sea,” he said, in a recent public statement.
“Ratification will bring significant benefits to the kingdom of Cambodia as a maritime nation” he added.
Thai media reported that Thai Prime Minister Anutin Charnvirakul has confirmed that Bangkok is preparing to revoke the 2001 maritime memorandum of understanding with Cambodia, known as MoU44, citing a lack of progress after more than two decades of negotiations.
The agreement, signed in Phnom Penh in June 2001, was designed to manage overlapping claims in the Gulf of Thailand through a “package deal” approach — combining boundary delimitation with joint development of offshore oil and gas resources.
But the Thais now argue it has failed to deliver tangible outcomes and has instead prolonged disputes.
Thai government spokesperson Rachada Dhnadirek noted that only five formal negotiation rounds had taken place in 25 years, with no concrete resolution.
Thai authorities are now proposing to rely on Unclos as the primary legal framework for future negotiations.
The ratification comes at a sensitive time.
Former diplomat Pou Sothirak noted that the 2001 bilateral arrangement was forged during a period of strong political goodwill between the two countries, allowing both sides to pursue joint resource development without prejudicing sovereignty claims.
“At that time, there was mutual understanding and political will to solve overlapping claims through joint development,” he explained.
“We agreed not to take each other’s sovereignty over their waters and to share benefits,” he said.
However, he noted that the MoU has remained largely inactive for more than two decades.
“Until now, Thai side thinks that the MoU 2001 has not been implemented in any concrete form. There have been no meetings and no agreements,” he added.
Thailand is now reviewing the agreement, partly due to domestic political considerations and unresolved land boundary disputes that have spilled over into maritime claims.
“According to Thailand, the termination of the MoU is linked to land border issues. These disputes extend to the sea because the overlapping maritime area is also tied to territorial sovereignty,” said Sothirak.
Against this backdrop, Cambodia’s embrace of Unclos signals a shift towards a multilateral, rules-based framework.
“What Cambodia has in Unclos is not a bilateral agreement,” Sothirak stressed, adding that “It is a maritime constitution adopted by the international community to resolve disputes on a global scale.”
He added that Unclos places Cambodia and Thailand on equal legal footing.
“Anything that Thailand has as a right protected by Unclos, Cambodia has the same right. We now stand on equal ground under international law,” he said.
The implications are significant, particularly in scenarios involving unilateral actions in disputed waters.
Sothirak suggested that according to Thailand, the MoU 2001 was terminated because of a border dispute with Cambodia on land.
According to a map drawn by unilateral, Thailand claims that some areas on the border are its territory.
“Because of this land dispute, it extends to the sea, because the area covered by MoU2001 is also a problem related to territorial sovereignty between Cambodia and Thailand,” he said.
“To put it simply, it is a defeat for Thailand because it claims those lands as its land, but it has already lost several cases at the ICJ (International Court of Justice) on the territory of the Preah Vihear temple,” he added.
Therefore, he believed the Thais appear to be attempting to alter every bilateral agreement, whether MoU2001 or MoU2000, either terminating them or adjusting the details.
“If Thailand were to drill unilaterally in an overlapping claim area, Cambodia can object and bring a legal complaint,” he said.
“Unclos contains provisions that prevent such unilateral decisions. It protects our sovereign rights,” he added.
Legal experts say Unclos provides Cambodia with a clear and comprehensive framework to define and exercise its maritime jurisdiction.
Researcher Dany Channraksmeychhoukroth described the convention as an international treaty that governs all activities in oceans and seas while promoting equitable resource use and peaceful cooperation.
“It establishes a specific and comprehensive legal framework to govern maritime activities,” she said.
Under Unclos, Cambodia exercises full sovereignty over its internal waters and territorial sea, which extends 12 nautical miles from its baseline.
Beyond that lies the contiguous zone, where authorities can enforce laws related to customs, taxation, immigration and sanitation.
The Exclusive Economic Zone (EEZ), extending up to 200 nautical miles, grants Cambodia sovereign rights to explore and exploit natural resources, including fisheries and hydrocarbons.
“We have the right to explore, exploit, conserve and manage both living and non-living resources in this zone,” Chhoukroth told state-run outlet TVK.
She added that Cambodia also holds rights over its continental shelf, allowing access to seabed resources such as minerals without the need for physical occupation.
A key advantage of Unclos is its structured system for resolving maritime disputes through international legal mechanisms.
These include arbitration panels and institutions such as the International Tribunal for the Law of the Sea and the International Court of Justice.
“Unclos provides mechanisms for peaceful dispute settlement, including both voluntary and compulsory procedures,” Chhoukroth said. “This ensures that disputes can be resolved based on law rather than power.”
She noted that the complexity of maritime boundary delimitation was one of the reasons Unclos negotiations took 15 years to complete between 1967 and 1982.
With a coastline of around 400km, Cambodia stands to gain significantly from the legal certainty provided by Unclos.
The convention strengthens protections over marine resources, including fisheries and potential offshore oil and gas reserves, while also promoting environmental conservation.
“Unclos ensures protection under international law for resource management, marine scientific research and environmental conservation,” said Chhoukroth.
It also opens the door to technical cooperation and technology transfer from other member states, as well as participation in global maritime governance bodies.
For Cambodia, officials and analysts say the value of Unclos extends beyond technical legal definitions.
Sothirak likened the convention to an “insurance policy” for the Kingdom’s maritime interests.
“The law will judge based on evidence and proof,” he told The Post. “This ensures that Cambodia’s resources and rights remain protected under international standards.”
As regional dynamics evolve and questions linger over bilateral arrangements with Thailand, Cambodia’s accession to UNCLOS is increasingly seen as a strategic move to anchor its maritime claims within a globally recognised legal framework.
“In today’s context, having this legal protection is crucial,” Sothirak said. “It gives Cambodia clarity, equality and the ability to defend its rights on the international stage.” - The Phnom Penh Post/ANN
