The sudden military escalation between two ASEAN members, Thailand and Cambodia, has jolted the Indo-Pacific, a region that’s already on edge amid the Great Power contestation between the United States and China.
Now in its second day, the hostilities continue and a ceasefire remains elusive, if not impossible. The implications for regional stability and the broader US-China strategic rivalry—often dubbed ‘Cold War 2.0’—are already profound.
For observers in South Asia, the crisis strikes a familiar chord. Much like the subcontinent’s own post-colonial challenges, this conflict is deeply rooted in contested borders callously drawn by colonial powers. In South Asia, the legacy lies with the British; in Southeast Asia, it’s the French.
The timing couldn’t be more telling. Global military budgets are rising amid geopolitical strains, and Southeast Asia is no exception. Even as ASEAN countries pursue deeper economic integration—modelling aspects of the European Union—defence spending has surged across the bloc. This, even though ASEAN is far from unified in its political, economic, or military postures.
While the ASEAN Free Trade Area has made strides in tariff reduction, wide disparities persist. Singapore boasts high per capita income and advanced infrastructure, while countries like Cambodia, Laos, and Myanmar continue to struggle with poverty, fragile institutions, and uncertain futures. The World Bank recently revised Cambodia’s 2025 growth forecast down to 4 per cent, citing a range of economic vulnerabilities.
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Fragmented security postures
In security terms, ASEAN remains a mosaic of national agendas, even in the face of China’s aggressive build-up in the South China Sea and its expansive nine-dash line claims over the EEZs of several member states. A common threat should have united the bloc. But as China is also ASEAN’s largest trading partner, siding against it remains unaffordable for most, even those with a pro-West tilt.
Military modernisation is progressing, but along divergent paths. Between 2013 and 2022, the region spent approximately $60.9 billion on weapons procurement and defence R&D, according to the International Institute for Strategic Studies (IISS). But looking closer, these investments reflect broader geopolitical alignments: some countries lean toward the US, like Thailand and the Philippines; some toward China, such as Cambodia, Laos, and Myanmar; and some are building ties with Russia, such as Vietnam and Indonesia. The presence of the UK and France, as well as the growing influence of Turkey and Israel in the region, adds further layers of complexity.
From imperial maps to military clashes
Southeast Asia has long been a stage for Great Power rivalry. The roots of the current Thailand-Cambodia conflict lie in the 1907 Franco-Siamese Treaty. Under pressure from both Britain and France, Siam (modern-day Thailand) ceded territories to the French. At the time, Cambodia was under French rule, and the treaty left many areas of the border vague—sowing the seeds of future disputes.
During World War II, Siam allied with Japan and briefly regained some of the lost territory. But following Japan’s defeat, these areas returned to French control. When Cambodia gained independence in 1953, the problematic colonial borders remained.
One hotspot is the Preah Vihear Temple. Though the International Court of Justice awarded it to Cambodia in 1962, the surrounding territory was left undefined, allowing the conflict to simmer.
The Cold War further complicated the picture. Cambodia’s civil war, the Khmer Rouge regime, and Vietnam’s 1978 invasion turned the Thai-Cambodian border into a Cold War flashpoint. The US, China, and several ASEAN members supported anti-Vietnamese resistance, including remnants of the Khmer Rouge. Even after Vietnam withdrew in 1989, and the 1991 Paris Peace Accords attempted to stabilise the region, no durable border resolution was reached.
Efforts at rapprochement resumed in the 2000s, culminating in a February 2024 strategic partnership between Cambodia and Thailand focused on de-escalation. But on 28 May 2025, a deadly clash between patrols in a disputed area killed a Cambodian soldier, shattering the fragile peace.
Since then, serious escalation has happened.
New theatre for the new Cold War?
In the ongoing military standoff, Thailand has clearly dominated from the get-go. The skies over Southeast Asia quickly became a theatre of conflict, with Thailand deploying its F-16 fighter jets and reportedly decimating Cambodia’s 8th and 9th infantry divisions. For the first time, Thailand also fielded its Ukrainian-made T-84 Oplot-M main battle tanks in combat, facing off against Cambodia’s outdated T-55s. The disparity in military capabilities between the two countries is not merely significant—it is exponentially vast.
Cambodia’s decision to escalate, despite its weaker military, raises questions. One possible explanation is Chinese backing—part of a broader strategy to test the limits of US commitment to its allies. US arms sales, including to Thailand, are governed by strict end-use agreements that limit how and against whom they can be deployed. It is unlikely Thailand would have used F-16s without prior US consent.
If true, this suggests Washington tacitly approved Thailand’s response—a subtle yet pointed signal to Beijing, which has become Cambodia’s chief military patron since 2017. After Cambodia dissolved its main opposition party and jailed political leaders, the US slashed aid. China quickly stepped in with military equipment, training, and joint exercises such as ‘Golden Dragon’.
More concerning is China’s role in expanding the Ream Naval Base on Cambodia’s southern coast. Though not officially a military base, satellite imagery shows a pier nearly identical in length and design to one at China’s Djibouti base—capable of docking its largest aircraft carriers. US officials have repeatedly raised concerns about growing Chinese military access to the base.
These developments may explain why Washington allowed Thailand to respond forcefully—viewing it as an opportunity to counterbalance Chinese influence.
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The wider web of power projection
This conflict must also be understood in the broader context of foreign power projection in Southeast Asia.
The US has deepened ties with the Philippines, now one of ASEAN’s most hawkish voices on China. Meanwhile, the UK exerts influence through the Five Power Defence Arrangements (FPDA)—a long-standing, though non-binding, security pact with Australia, New Zealand, Malaysia, and Singapore.
This agreement, notably, was originally designed to ensure peace between Malaysia and Singapore. For the uninitiated, on 9 August 1965, Singapore officially parted ways with Malaysia, becoming an independent and sovereign nation. The split was driven by serious political and economic disagreements between the leadership of both countries, which had fuelled communal tensions and led to racial riots in July and September 1964. Although those tensions have long since eased, the UK continues to maintain its involvement through existing defence agreements and regular military exercises.
France, another former colonial power, also maintains a strategic presence in the Indo-Pacific. It often champions “strategic autonomy,” positioning itself as a balancing force in a region crowded with competing powers—though it would side with NATO allies if a hot war broke out.
Even intra-ASEAN military tensions carry geopolitical implications. Indonesia, for example, has long struggled to fully control its airspace, as parts of it—including the skies over the Riau Islands and the Strait of Malacca—are under Singaporean operational control. Jakarta is now addressing these concerns by upgrading its air defence capabilities, including a $10 billion deal for Turkish-built KAAN fifth-generation fighter jets, which will involve significant contributions from Pakistani engineers. It has also ordered a huge number of Rafale jets from France, amid other equipment.
At its core, the Southeast Asian theatre remains central to the unfolding Great Power contest between the US and China (backed by Russia). But it is also a landscape where middle powers—France, the UK, Turkey, and others—continue to shape the strategic environment in nuanced but significant ways.
The Thailand-Cambodia escalation underscores not only the unresolved trauma of colonial legacies but also how quickly they can be weaponised in today’s fraught geopolitical climate.
As great powers manoeuvre and middle powers assert their influence, the Indo-Pacific grows more complex. With war now an ever-present possibility rather than a distant threat, Southeast Asia finds itself not just at the centre of Cold War 2.0—but at the frontline of an increasingly crowded, competitive, and dangerous global order.
Swasti Rao is a Consulting Editor (International and Strategic Affairs) at ThePrint. She tweets @swasrao. Views are personal.
(Edited by Asavari Singh)