By Kin Phea, PhD

Director General of the International Relations Institute of Cambodia

Cambodia and Thailand are predominantly Buddhist neighbouring kingdoms that share deep historical, cultural, and religious ties. Their land border, stretching over 800 kilometres, was originally defined by the Franco-Siamese treaties of 1904 and 1907.

Despite these shared affinities, tensions have frequently arisen, particularly over claims to cultural heritage, traditions, and religious sites, including temples. Disputes over territory and border demarcation have been among the most sensitive and inflammatory issues, often fuelling ultranationalist sentiments in Thailand for generations.

The most contentious areas include the Preah Vihear Temple and its surrounding vicinity, over which Cambodia secured legal victories at the International Court of Justice (ICJ) in both 1962 and 2013. Other disputed sites include Ta Moan Thom Temple, Ta Moan Tauch Temple, Ta Krabey Temple and Mom Bei.

The recent incident initiated by the Thai side on 28 May 2025 in Mom Bei, Preah Vihear province, deep within Cambodian territory, where a Cambodian soldier was shot dead by Thai soldiers, has stirred Thai society with claims that Cambodian forces violated Thai sovereignty. It has also emboldened Thai military elements, known for staging coups d’état, to push for a full-scale war with Cambodia.

In 2000, Cambodia and Thailand signed a Memorandum of Understanding (MOU) on the survey and demarcation of the land boundary between the two countries. Under this MOU, a Joint Border Commission (JBC) was established. The land boundary survey and demarcation have been jointly conducted in accordance with the Franco-Siamese Convention of 13 February 1904; the Franco-Siamese Treaty of 23 March 1907; the Protocol concerning boundary delimitation annexed to the 1907 Treaty; and the maps resulting from the work of the Commissions of Delimitation of the Boundary between Indo-China and Siam, established under the 1904 Convention and the 1907 Treaty. Other relevant documents relating to the implementation of the 1904 Convention and the 1907 Treaty between Siam and France are also taken into account.

However, the 2000 MOU has proven ineffective in resolving the issue, leading to frequent accusations and several armed conflicts. A key root cause of the conflicts is the use of different sets of maps. Cambodia, along with the ICJ, relies on maps established under the 1904 Convention and the 1907 Treaty. In contrast, Thailand unilaterally produces and uses its own maps to assert territorial claims.

In addition, border issues with Cambodia have often been strategically used by Thailand during periods of domestic political instability or when the military has sought to assert or consolidate power through a coup. A notable example occurred in 2008, when Thai forces entered Cambodia’s Preah Vihear Temple area and its surroundings, despite the ICJ’s 1962 ruling that the temple belongs to Cambodia. The armed conflict persisted for several years. More recently, the border clash last month at Mom Bei in Cambodia appears to be another instance of Thai military provocation, potentially aimed at justifying or facilitating a new coup.

With the 2000 MOU having reached its limits in resolving longstanding border disputes, the Royal Government of Cambodia decided on 2 June 2025 to refer the dispute over four sensitive areas - Mom Bei, Ta Moan Thom Temple, Ta Moan Tauch Temple, and Ta Krabei Temple - to the ICJ. These areas have remained unresolved for years and continue to pose risks of heightened tensions if left unaddressed. The decision was unanimously endorsed by the First Joint Congress of Cambodia’s National Assembly and Senate, and the strongest support of all Cambodian people at home and abroad and all political groupings.

As the larger country in terms of economic and military capacity, Thailand has consistently favoured bilateral negotiations, an approach that tends to serve its strategic interests. In contrast, Cambodia remains committed to utilising all available mechanisms deemed necessary, particularly turning to the ICJ when bilateral efforts are exhausted.

Thailand has exerted both military and economic pressure on Cambodia, including the deployment of additional troops and military equipment along the border. Furthermore, it unilaterally closed several border checkpoints on 7 June 2025, a recurring tactic used as an economic lever, given Thailand’s stronger economic position.

Such unilateral closures, employed repeatedly over time, reflect a zero-sum approach that carries significant economic risks for both countries and undermines efforts toward long-term stability and cooperation.

If Thailand is genuinely committed to resolving the border issue peacefully, it should cooperate with Cambodia in pursuing impartial, rules-based mechanisms, such as referring the matter to the ICJ, once bilateral negotiations have been exhausted. As a smaller country in terms of geography, population, economy, and military strength, Cambodia has neither the capacity nor the intention to provoke conflict or invade any of its neighbours. The Kingdom seeks peaceful co-existence, regional cooperation, and friendly relations as essential foundations for national development and shared prosperity.

Historically, Cambodia was a great empire long before the emergence of Thailand as a state. Much of what is now Thai territory was once part of the ancient Khmer Empire. Thailand began to assert its independence from Khmer influence in the 13th century, eventually evolving into a distinct state thereafter.

Therefore, the people of Cambodia and Thailand should recognise that our two nations share a long history, along with deep cultural and traditional affinities. At the same time, it is important to understand that our territorial boundary is a legacy of the colonial era. In the aftermath of World War II and with the achievement of independence, both countries must adhere to the international legal principle of uti possidetis juris, which affirms that colonial-era borders, as defined by the Franco-Siamese treaties, must be respected. Failing to do so risks perpetuating an endless cycle of conflict.

To the Thai military, political leaders, and people: history should not be distorted for future generations. It is essential to acknowledge historical realities and educate the public to respect the sovereignty, territorial integrity, dignity, and cultural identity of neighbouring countries. Only through mutual respect and a commitment to a culture of peace and harmonious co-existence can our two Buddhist kingdoms truly live side by side in peace.