When Thailand and Cambodia reopened fighting along their 817-kilometer border, the question was not just who would stop the weapons, but who in Southeast Asia could afford it. The fighting in July 2025 ended with a ceasefire agreement, with Malaysia acting as ASEAN chair at the time and helping to mediate it. Then in December 2025, the battle heated up again after the October peace agreement mediated by the involvement of the United States failed. The clashes have killed at least 20 people and displaced about 600,000 people in both countries, so since then, the ASEAN Observer Team (AOT) has been monitoring the ceasefire (The Vibes, 2025).
The authors argue that the Asean Observer Team (AOT) is the most concrete step taken by ASEAN in the military dimension of regional security in recent years, but its limitations in remaining a mechanism that only monitors rather than prevents this make conflicts in the region persistent and difficult to avoid or resolve. This article will examine three main aspects: how the AOT was formed and what it actually does, why its reach is still limited by the ASEAN Way, and what ASEAN, especially Indonesia, must do to transform these observations into a real-impact preventive capacity.
Discussion
From Temporary Mission to Permanent Presence
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The ASEAN Observer Team (AOT) itself was initially started as a temporary arrangement only, wherein in August 2025, an interim team led by Malaysia with 14 representatives from eight ASEAN member countries conducted inspections in border areas in three Thai provinces, after a ceasefire reached at a special meeting of the General Border Committee in Kuala Lumpur (Intellinews, 2025). The mission is currently led by the Philippines as the current chair of ASEAN, with a mandate to observe, verify, and report on the implementation of the agreement between the two countries (Free Malaysia Today, 2026). To date, its membership continues to grow; Singapore and Malaysia added their officers in March 2026, and Laos also sent two military officers in July 2026 (Asia News Network, 2026; Phnom Penh Post, 2026).
This is noteworthy, because with military officers from ASEAN countries deployed to monitor disputes between the two ASEAN members, it is a form of defense cooperation that the bloc’s declaration has long promised but is very rarely kept. Acharya (2001) argues that ASEAN’s claim as a security community depends on “Can members manage conflicts among themselves without outside arbitration?” as the AOT has been one of the closest tests of such claims in recent years (Acharya, 2001).
The Limits of Watching
However, the test was only partially missed, where the observers did not cross the border, and they only worked from within each country (GMA News, 2025). On the Cambodian side, for example, inspections were coordinated through Cambodia’s own liaison groups, and Phnom Penh used this visit to reaffirm its position that no border change could occur as a result of the use of force (Khaosod English, 2026). Therefore, this mission documents what each host demonstrates, rather than independently establishing the facts on both sides of the disputed line.
Meanwhile, the political settlement is more influenced by some outside pressure than ASEAN. Reuters itself reported that the two new leaders rose to the negotiating table after the United States linked the tariff negotiations to peace (GMA News, 2025). Thailand itself is on its side, as it has historically rejected international mechanisms such as the International Court of Justice and demanded bilateral negotiations (Free Malaysia Today, 2026). This is the ASEAN Way at work: through consensus, non-intervention, and respect for the consent of the parties (Haacke, 2003). The AOT exists because both governments agree to it and can only do what both governments allow.
Critics may object that the AOT’s simple mandate is precisely the main reason for its existence, where both governments accept observers, and that a stronger mandate could make the mission lose the approval on which they rest. These concerns are very justified, especially given Thailand’s preference for bilateral negotiations (Free Malaysia Today, 2026). But the mission’s steady expansion from 2025, with more officers joining from more member states, suggests that confidence in this mechanism has grown, not faded. The proposals below, therefore, do not ask for new powers over the two governments; they simply ask ASEAN to formalize, before and with the consent of both sides, what the observers have already done.
From Observation to Prevention
If the AOT wants to be more than just a witness, then ASEAN needs to move from trust-building to preventive diplomacy, while still working within consent-based norms that its members will not abandon. The security community itself is judged on whether its members are capable of managing disputes among themselves, and such standards also require pre-crisis capacity, not just post-crisis comments (Acharya, 2001). There are three realistic steps that can be taken:
First, institutionalizing the mission. Currently, the AOT’s leadership still follows rotating chairs, so its continuity also depends on the priorities of each chair. A permanent arrangement under the framework of the ASEAN Defense Ministers’ Meeting, with a permanent coordination table, would prevent expertise from being reset every January. It would also give observers a stable channel to the defense ministry, rather than leaving that relationship to whichever country holds the chairmanship.
Second, make incident reporting two-sided and routine. A joint verification protocol, which has been agreed upon in advance by the two governments, will allow observers to respond to allegations of violations quickly, rather than after tensions have escalated. Through joint reporting, it will also reduce the risk that each party’s accounts will become the only accounts available, which is often the cause of small incidents developing into larger ones.
Third, it offers technical assistance in demarcation designed to respect Thailand’s preferences in bilateral talks. Most of the borders were first mapped under French colonial rule in 1907 (GMA News, 2025), and the unmarked parts are the root of the problem here. A joint mapping supported by ASEAN would address the causes, not just the symptoms, as this work is technical rather than political, so both governments may be easier to accept than with proposals that resemble arbitration.
Indonesia itself is actually a country that is in a good position to support these measures, as Indonesia has provided an observer to the interim team in 2025 (Intellinews, 2025) and has a long track record as a norm entrepreneur in ASEAN. As a founding member who is not involved in this dispute, Jakarta (the capital of Indonesia) can credibly display a stronger AOT as a collective interest of ASEAN than a national agenda, and one that is consistent with its own interests in a stable region.
Conclusion
The ASEAN Observer Team shows that defense cooperation in Southeast Asia is no longer just about the communiqué, because at the same time, they reveal the extent to which the bloc’s security culture still limits what the cooperation can achieve. Observers who cannot cross the border and rely solely on the agreement of the two sides certainly cannot stand in the way of much on their own. The real choice for ASEAN is whether the ASEAN Observer Team (AOT) remains a temporary arrangement that relies solely on the country holding the chair or whether it will be the foundation of a more credible deterrence capacity. If the bloc is still unable to strengthen the mission already accepted by both governments, then it is difficult to imagine how they will act in a dispute where agreement is harder to win, so the Thailand-Cambodia border will be a testament to that in both decisions.
