Thailand's decision to cancel the memorandum of understanding on overlapping maritime claims with Cambodia, widely known as MoU 44, marks a major shift in how both countries will manage maritime tensions in the Gulf of Thailand 25 years after it was signed in 2001.
The decision of the Anutin Charnvirakul administration to adopt the United Nations Convention on the Law of the Sea (UNCLOS) in place of the scrapped MoU may hint at further unpredictability ahead as bilateral talks make way for internationally endorsed recommendations that are void of any legal bindings.
Why MoU 44 became controversial
MoU 44 was originally designed as a framework for negotiating maritime boundaries and establishing a Joint Development Area (JDA) between Thailand and Cambodia.
In 2001, the Exclusive Economic Zone (EEZ), a framework Thailand set up in the 1980s, suggested the 26,000-square-kilometre Overlapping Claims Area (OCA) in the Gulf of Thailand could contain commercially valuable oil and gas reserves.
At the time, both countries sought a pragmatic solution that would allow economic cooperation to proceed despite unresolved sovereignty disputes.
Both governments are encouraged to pursue joint development while temporarily setting aside territorial disagreements, leading to the signing of the MoU.
However, critics argued the agreement carried structural weaknesses.
Dr Dam Sukontasap said one key concern was that the memorandum implicitly acknowledged the possibility of a Thailand-Cambodia JDA based on maritime boundary assumptions that may not fully align with international legal principles.
On the other hand, MoU 44 risked weakening Thailand's long-term negotiating position over overlapping maritime claims.
Why UNCLOS matters now
The shift towards the adoption of UNCLOS comes as Southeast Asia faces increasing pressure from energy disruptions, geopolitical tensions and economic uncertainty.
As Thailand pushes its Eastern Economic Corridor ambitions, both Thailand and Cambodia are seeking greater energy security as volatility in global oil and gas markets affects the region.
Critics say offshore energy development could generate substantial economic benefits for both countries through state revenue, reduced import dependence and long-term industrial growth.
Unresolved maritime disputes also create legal uncertainty that can discourage international investors from committing to offshore exploration and large-scale infrastructure projects.
By invoking compulsory conciliation under UNCLOS, Cambodia is moving the dispute into a more structured international legal process rather than relying solely on bilateral diplomacy.
Although both countries are already parties to UNCLOS, the conciliation mechanism introduces a formal rules-based framework for reviewing overlapping maritime claims. While the recommendations are not legally binding, the process carries diplomatic and reputational weight internationally.
Panitan Wattanayagorn, an international affairs expert, said Cambodia could potentially gain advantages from the process due to its stronger international alliances.
How will both sides talk now?
Both sides agreed to begin a gradual process of talks at all levels, including under the bilateral JBC (Joint Boundary Commission) and GBC (General Border Committee) frameworks and through discussions between the foreign ministers, to create shared benefits for the people of both countries.
The negotiations will discuss the ceasefire agreement and the guidelines previously agreed upon to build an atmosphere of peace and mutual trust.
A direction is steering towards strengthening peace and stability between Thailand and Cambodia.
What are the regional implications?
The dispute also carries wider implications for Asean and regional maritime governance, critics said.
A stronger reliance on UNCLOS mechanisms may reinforce Asean's preference for international law in managing regional disputes, particularly in the South China Sea. Vietnam is expected to monitor developments because of its own maritime tensions with China.
Malaysia could benefit from improved maritime stability along the Gulf of Thailand and Strait of Malacca trade routes, although future offshore energy development by Thailand and Cambodia may create greater regional competition in gas exports and energy investment.
For China, wider Asean reliance on international legal mechanisms could strengthen maritime legal norms that challenge Beijing's broader territorial claims, even as greater regional stability may support Chinese investment interests across Southeast Asia.
How will UNCLOS help Thailand?
It could provide both strategic and economic advantages.
A clearer legal structure governing overlapping maritime claims may strengthen energy security by unlocking access to offshore natural gas and petroleum reserves.
Greater legal certainty could also improve investor confidence and support new infrastructure and energy-related investment.
Beyond energy, the process could improve bilateral relations with Cambodia, strengthen maritime stability in the Gulf of Thailand and reinforce Thailand's international standing as a supporter of rules-based dispute resolution.
The longer-term opportunity may lie in creating conditions for joint development in energy, fisheries and maritime industries without requiring an immediate resolution of sovereignty disputes -- a balance both countries have struggled to achieve for over two decades.
