Malaysia and ASEAN will have limits on Thailand and Cambodia - Just as the US does

This moment marks a turning point—not only for Thailand and Cambodia but for ASEAN and its external partners. The image of a leader tearing up a peace declaration on the very soil where landmine blasts have occurred sends a grim message: regional diplomacy has met its limits, and non-state actors may have just won another round.

The ceasefire that once promised to halt hostilities was built on delicate scaffolding. It rested on a trilateral understanding between Thailand, Cambodia, and mediators—principally Malaysia and the United States. But the agreement underestimated how deeply entrenched local conflicts remain across the rough terrain of the border.

Prime Minister Anutin’s inspection of both old and new landmines confirms what analysts have feared: that the ceasefire’s biggest threat was never high politics but the battlefield’s low-intensity violence, sustained by militias, smugglers, and rogue networks beyond either government’s control. These non-state actors have long blurred the line between crime and insurgency, and in doing so, have made peace unenforceable. The blasts in recent weeks—one maiming a Thai soldier—represent not only physical damage but political corrosion. They harden national sentiment, erode trust, and turn public patience into rage. When the pain is literal, diplomacy becomes abstract.

ASEAN’s mediation capacity has always rested on persuasion rather than enforcement. Malaysia’s chairmanship this year gave the bloc credibility, as Kuala Lumpur brought both parties to the table in October. Yet, ASEAN’s strength—its consensual diplomacy—is also its constraint. When one party tears up a declaration, there is no collective mechanism to compel compliance.

The United States, despite having co-sponsored the peace effort under President Donald Trump’s renewed Indo-Pacific push, faces its own limitations. Washington cannot deploy peacekeepers, nor can it risk appearing to take a military side in one claimant's favour against another. Hence, both ASEAN and the US are left urging restraint from capitals that no longer listen.

Anutin’s explicit remark that Thailand “will not report to Trump” signals a deliberate assertion of sovereignty. Bangkok is sending a message that while external mediators may facilitate dialogue, they cannot dictate outcomes. This mirrors the broader trend in Southeast Asia, where national pride often outpaces institutional cooperation.

Phnom Penh, for its part, maintains it has not violated the peace deal, insisting the mines discovered are relics of earlier wars. But the asymmetry in political and military narratives is widening. Thailand’s outrage has turned the ceasefire from a symbol of ASEAN diplomacy into a symbol of its impotence.

Cambodia, historically sensitive to Thai military incursions, will now interpret Thailand’s withdrawal as a pretext for unilateral border patrols. The cycle of accusation and retaliation risks returning the region to the chaotic summer of 2025, when over 300,000 civilians were displaced within days.

Malaysia and ASEAN have long believed that with enough dialogue, even old animosities could be contained. Yet, what is unfolding now is a stark reminder that containment is not control. Border security, like peace itself, depends on the micro-mechanisms of enforcement—mine clearance, patrol coordination, and command discipline.

When Prime Minister Anutin tore up the Kuala Lumpur Declaration, he did more than reject Cambodia’s credibility; he exposed ASEAN’s structural vulnerability. The bloc can mediate, but it cannot monitor. It can convene, but it cannot coerce.

Even the United States, which once prided itself on being the “offshore balancer” of Southeast Asia, has little appetite for another diplomatic quagmire. Washington’s influence is waning precisely because the conflict has slipped below the threshold of state-to-state negotiation. The battlefield is now controlled by the unpredictable—the remnants of past wars and the opportunism of border-based networks.

The collapse of the Thai Cambodian ceasefire carries three painful lessons for ASEAN.

First and foremost, peacebuilding must be local, too, not just legal. Regional declarations mean little if border communities remain militarized and impoverished.

Secondly, ceasefires without demining are a false peace. Until both sides commit to a verified demining program, accidents will be mistaken for aggression.

Thirdly, diplomacy without deterrence breeds defiance. Neither ASEAN nor the US can prevent escalation without credible post-agreement enforcement tools—something ASEAN has avoided for decades.

Malaysia’s role as ASEAN Chair remains critical but limited, as it ends on December 31, 2025, although both sides have enlisted Prime Minister Anwar to keep the mediation going.

To be sure, Anwar Ibrahim can still call for an emergency ASEAN Troika meeting to re-establish communication channels. Yet even such diplomacy may amount to managing symptoms rather than resolving causes.

When Anutin declared “Peace is over,” he was not merely venting nationalist fury. He was expressing a truth that has haunted ASEAN since its founding in 1967: that sovereignty, not solidarity, defines Southeast Asia.

Both Thailand and Cambodia are now captive to forces of their own making—national pride, non-state sabotage, and institutional fatigue. Malaysia and ASEAN, like the US, can mediate but not mend. The region’s peace is ultimately only as strong as the will of its weakest frontier.

Unless ASEAN learns to move beyond declarations toward sustained, enforceable conflict management, peace in mainland Southeast Asia will remain what it has always been — a temporary truce written on fragile paper, waiting for the subsequent explosion to erase it.