The Cambodia–Thailand Conflict: What Implications and Consequences for ASEAN?

While relations between Thailand and Cambodia appear to be easing, it seems timely to revisit the significance of these events for the Association of Southeast Asian Nations (ASEAN). On 24 July 2025, armed clashes broke out between the two countries, the expression of tensions simmering since the beginning of the year and which escalated at the end of May. Stemming partly from a long-standing dispute over the demarcation of their shared border, the conflict caused the deaths of some forty people and the displacement of around 300,000 in just a few days. Although the previous confrontation between the two countries in 2011 had also resulted in some forty deaths, this new escalation surprised observers by its violence, breaking with the long-championed “ASEAN Way” and the “peace” it upheld. What are the short- and long-term impacts on the regional organisation? What does this crisis reveal about ASEAN? Insights from Christine Cabasset, PhD in Geography, associate and former Deputy Director of the Research Institute on Contemporary Southeast Asia in Bangkok, and associate of IRIS’s Asia-Pacific programme.

If this is not the first incident between the two countries, can we expect this new episode to have negative consequences for ASEAN’s image and centrality?

Let us first recall that since its formation in August 1967, ASEAN has faced numerous crises that have led some observers to question whether the organisation could recover. This was the case, for example, during the 1997 Asian financial crisis and its aftermath. The regional association not only recovered but has since greatly strengthened its foundations, credibility and attractiveness. The world has become accustomed to seeing ASEAN as a space of stability, far from the conflict zones and violence of other regions such as the Middle East, or the demographic and economic pressures of the giants India and China.

In the current crisis, it is no coincidence that Malaysia – backed by China and the United States – was able to mediate between Cambodia and Thailand, securing a ceasefire on 28 July, renewed on 7 August (together with the principle of ASEAN observers being stationed on both sides of the border): this aligns with the role expected of ASEAN’s chair, which Malaysia holds in 2025. Furthermore, Prime Minister Anwar Ibrahim, active on both the regional and international stage, has promoted the idea of a Muslim world as a political force internationally and of a democratic Muslim Malaysia. Beyond that, it is worth recalling that Malaysia, Indonesia, the Philippines and Singapore (as well as Brunei, which held the ASEAN chair in 2021) had already taken up the Burmese question following the coup d’état of February 2021, before East Timor became particularly outspoken on the issue from 2022. That said, it is precisely because the regional bloc failed to influence the Burmese crisis that this new episode delivers a blow to ASEAN’s “centrality.”

Given that ASEAN has stalled on resolving the Burmese crisis, can one still be optimistic about the outcome of the Cambodia–Thailand dispute? What historical role has ASEAN played in stabilising conflict in Southeast Asia? What are its present limits?

This is a test that could tarnish ASEAN’s image by highlighting its main weakness: its difficulty in addressing political crises, particularly those relating to conventional security such as this bilateral conflict. The region’s history, heavily marked by coups d’état and authoritarian regimes, provides many examples of ASEAN’s inability to respond. When in 1965–1966, in Indonesia, the murderous anti-communist purge (at least 500,000 deaths) brought to power the country’s new strongman, General Suharto, he not only ruled the vast archipelago with an iron fist (1967–1998) but also exerted considerable influence on ASEAN throughout his 32 years in power. In 1967, and until the mid-1990s, ASEAN comprised only the five founding members – Indonesia, Malaysia, the Philippines, Singapore and Thailand (joined by Brunei upon its independence in 1984) – federated initially as an anti-communist front. This partly explains why, in the Cold War context, Indonesia’s invasion in December 1975 of Portuguese Timor, then on the verge of independence following Portugal’s Carnation Revolution (April 1974), and its annexation as the 27th province of Indonesia (until 1999), met with no reaction from ASEAN. Even when considering much more recent crises, the conclusion remains the same. Thailand, for instance, subject to violent political crises (1992 and 2010) and regular coups (2006 and 2014 being the most recent): here too, in the name of non-interference in internal affairs, ASEAN remained silent. Other examples could be drawn from the environmental sphere (almost annual toxic haze from massive forest fires, and other episodes of air and water pollution), with the regional organisation struggling to denounce the causes and to take drastic measures.

All this relates to the ASEAN Way which, in addition to non-interference, rests on key principles such as consensus – in practice requiring unanimity – and compromise. Since accession to ASEAN entails few binding frameworks or documents, and the bloc has not pushed regional integration to the point of creating a supranational body, unlike the European Union, adherence to these principles relies largely on goodwill. It should also be noted that the ASEAN Charter (2007) commits to ensuring that peoples and member states live in a just, democratic and harmonious environment (Article 1.4), but it does not include concrete tools against coups, human rights abuses or cross-border conflicts. Moreover, while the Charter sets out rights and obligations (Article 5), as well as the procedures and criteria for admitting new members (Article 6), it does not articulate the notion of sanctioning a member that violates established principles. Thus, the suspension from 2021 of the military junta’s official representation at major events such as summits represented a highly significant step in the ASEAN context.

To avoid oversimplification, it should be added that ASEAN’s functioning is less rigid than it may appear. Despite the principle of non-interference, the organisation has shown an ability to cooperate in non-conventional security areas – humanitarian assistance and disaster relief, for example. Moreover, it has been represented by some of its members in the deployment of peacekeeping forces, as in Cambodia (early 1990s), East Timor (1999–2002) and Mindanao in the Philippines (1990s).

Given the rarity of bilateral conflicts in Southeast Asia and therefore the unusual nature of the Cambodia–Thailand conflict, does the regional organisation also not play a stabilising role?

Yes, certainly. Stability is ASEAN’s great strength and this is what makes the regional organisation remarkable. For, let us remember, ASEAN’s path to peace and cooperation was far from easy. Just as the European Union was forged by the traumas of the Second World War, ASEAN was also forged in war: the Second World War, Japanese colonisation, the Vietnam War, the domino theory, the Cold War. It suffered particularly from its geographical position – and its ideological partition – between the two great blocs. The Bangkok Declaration, ASEAN’s founding text (8 August 1967), sets out objectives of economic growth, social progress, the promotion of peace and regional stability. This was significant, for at ASEAN’s founding the organisation was still riven by deep divisions and tensions linked to the “Konfrontasi” (1962–1966) between Indonesia, Malaysia, the Philippines and Singapore over the status and sovereignty to be exercised over northern Borneo (today’s Malaysian states of Sarawak and Sabah and Brunei Darussalam), while the rest of the island, Kalimantan, belongs to Indonesia.

The decision taken at the end of the Cold War to integrate into ASEAN the four “communist” countries – the CLMV (Cambodia, Laos, Myanmar and Vietnam) – was pragmatic. But the gesture was equally powerful, given the immense political and economic difficulties involved in bringing together all the Southeast Asian states. This was at a time when mistrust best characterised relations between the two blocs: Thailand had served as a rear base and played an active role in the struggle against communist Vietnam; Vietnam’s invasion of Cambodia in 1978, though it ended the Khmer Rouge regime, entrenched divisions through its decade-long occupation (until 1989). It should also be added that the eleven countries of this ensemble – including Thailand, the only one never colonised – had to contend with borders inherited from British, French, Dutch and Portuguese colonisations, which remain today the subject of disputes and negotiations. Although the factors behind the current Cambodia–Thailand confrontation are multiple, border demarcations are one of the recurrent flashpoints in relations. Recalling these elements allows for a better understanding of what establishing cooperation among these states and achieving regional consensus has entailed. ASEAN as an organisation, as well as its member states, has nevertheless managed to overcome these challenges, to forge peaceful – if not always trusting – relations, and to work towards maintaining stability. There is no doubt that the regional organisation is fully aware of the stakes of the current bilateral confrontation and is active on the issue: at this point in history, ASEAN and the region would have too much to lose if the conflict were to escalate.