Sovereignty’s Supremacy: Realism and the Deadly Thai-Cambodian Border

By: Isobel Garner 

Editor: Bronwen Smith 

Editor-in-Chief: Grace Samuel 

The views expressed are the author's own and do not reflect the views of the International Relations Society. 

Wikimedia commons, photo credit HansenHimself (Creative Commons 4.0) 

‘Thailand launches airstrikes on Cambodia as Trump’s peace agreement hangs in the balance’ screams the headline of CNN's first news report of the renewed tensions along the Thai-Cambodian border. It suggests a familiar story: another flare-up, another failed diplomatic effort, another fatality. Yet this assumption of global familiarity hides a deeper question. How can a border dispute that began in 1907 still be just as lethal today? With over 58 people dead in 2025 alone, what does this enduring violence reveal about the limits of international law and regional cooperation in resolving territorial conflicts, when viewed through the lens of realism? 

At the heart of the conflict lies the 508-mile border between Cambodia and Thailand, shaped by colonial ambiguity. When Cambodia was part of French Indochina, the ‘Annex I Map’ attempted to define the border between the two territories. Roughly drawn and imprecise, the map placed the 11^th century Preah Vihear temple on the Cambodian side, despite its drainage flowing northward into Thailand.  

Despite no formal objection from the Thai government at the time, the disputes began to intensify over the cultural and religious significance of the territory. The temples Prasat Preah Vihear and Prasat Ta Muen Thom, both of Hindu origin from the Khmer Empire, represent more than land. They are sites representative of cultural inheritance, historical legitimacy, and national prestige, stoking nationalistic intensityon both sides, and turning the border disagreement into a question of identity. This begins to explain why the dispute has periodically escalated into violence, first erupting in armed clashes in July 2008. 

That year, according to United Nations Cambodian ambassadors, ‘about 50 Thai soldiers moved into the Keo Sikhakirisvara Pagoda vicinity’, merely 300 metres from Preah Vihear, within Cambodia’s territory. Accusations of attempted Thai annexation followed, and skirmishes continued until April 2011, when clashes between troops left several dead. A unanimous decision to withdraw all troops from the disputed areas seemed the only solution. In May 2025, the death of a Cambodian soldier during a routine border patrol reignited hostilities, culminating in what The New York Times described as a 'brutal 20-day border war' in July, with over 500,000 people still displaced from their homes – a stark reminder of the human cost behind geopolitical rivalry.  

However, it is through the theory of political realism that a compelling explanation for this conflict is unearthed. Realism assumes an anarchic international system, through which states are rational actors seeking to preserve sovereignty and uphold security. Often cited as one of the forefathers of political realism, Thomas Hobbes’ seminal work Leviathan asserts that 'the war of all against all', made probable because of humanity’s inherent nature, could only be avoided by legitimate, powerful, and authoritative governments – something that simply does not exist at an international level.  

The attempts of international law to reach a permissible conclusion to the disputes were first examined in 1962, when the International Court of Justice (ICJ) ruled against Thailand’s unlawful occupation of Preah Vihear and ordered Thailand to withdraw all military personnel from Cambodian territory. Decades later, in 2011, Cambodia requested that the ICJ clarify its ruling by explaining the extent to which Cambodia could claim the territory surrounding the temple. As a result, in its 2013 ruling, the ICJ confirmed ultimate Cambodian sovereignty over the whole promontory. Yet, despite the legal clarity of these decisions, Thailand’s intermittent refusal to comply exposes a key political realism insight: international law lacks enforcement power. States often only adhere to legal rulings when they fully align with national interests. 

Regional diplomacy has faced similar constraints. Since 2013, The Association of Southeast Asian Nations (ASEAN) has played a mediating role, grappling with the struggles of keeping two of its member states from violence. The current chair, Malaysian Prime Minister Anwar Ibrahim, facilitated phone calls between the Cambodian and Thai Prime Ministers in order to encourage dialogue and peace. However, ASEAN’s strict adherence to the principle of non-interference means that state sovereignty reigns supreme, allowing ASEAN to manage tensions, but never fully resolve them. 

External intervention has fared no better. In late October 2025, US President Donald Trump presided over the signing of the 'Kuala Lumpur Peace Accord' witnessed solely by the leaders of both countries and the ASEAN chair. The accord’s primary success resulted in Trump even being nominated for a Nobel Peace Prize by the Cambodian Prime Minister. Despite the threat of increased tariffs from the USA if the agreement was violated, it collapsed within months. By December 2025, border clashes had resumed, resulting in further fatalities. From a realism perspective, the failure was predictable since diplomatic symbolism and economic pressure are insufficient to override entrenched concerns over sovereignty within a multipolar international system. 

Ultimately, the Thailand-Cambodia border dispute is not just a legacy of failed maps or discreet phone calls, but of a world where power overrules principle. Realism suggests that as long as sovereignty and national pride outweigh legal rulings and peace accords, even century-old borders can remain deadly fault lines. Until their interests align, peace along the Thai-Cambodian border is likely to remain signed on paper but contested on the ground.