Has Japan Lost in Southeast Asia?
Has Japan Lost in Southeast Asia?
#Opinion
What Cambodia-Thailand conflict reveals about Tokyo’s role in a Free and Open Indo-Pacific
Renewed fighting along the Cambodia–Thailand border has exposed an uneven diplomatic response among major powers—revealing not only who acted, but who chose restraint. The United States inserted itself through President Donald Trump’s peace-broker narrative, symbolic and transactional but designed to signal continued American relevance. China stepped forward with mediation “in its own way” and shuttle diplomacy, reinforcing its self-image as a regional crisis manager.
Japan’s response was deliberately limited. While Tokyo repeated familiar language on peace and international order, it avoided political engagement at a moment when such engagement mattered. This is not unusual for Japanese diplomacy. But in a live regional crisis, restraint is not neutral. When conflict unfolds in Southeast Asia, prolonged distance invites questions about whether Japan’s commitment to rules is situational rather than consistent.
This is not an argument that Japan bears responsibility for the Cambodia–Thailand conflict, nor is it a call for Tokyo to displace other powers. The question is narrower and more consequential: what happens to Japan’s regional relevance when conflict erupts close to home, and Tokyo chooses distance over presence?
Japan’s standing in mainland Southeast Asia rests on historical capital that few external partners possess. During the early 1990s, Japan played a leading role in supporting the United Nations Transitional Authority in Cambodia (UNTAC) and mobilising international backing for post-war reconstruction. Its engagement in Cambodia was neither coercive nor ideological; it was institutional, developmental, and sustained. Over time, this approach cemented Japan’s reputation as a dependable partner rather than a strategic opportunist. It also marked Japan’s re-emergence as a peace-promoting actor after its low-profile role during the Gulf War, when Tokyo sought to translate economic strength into diplomatic legitimacy.
That legacy matters because it shapes expectations. When violence re-emerges between two ASEAN members, Japan is not expected to lead militarily or impose solutions. But it is expected to engage politically, especially when its own diplomatic narratives emphasise stability, rules, and human security.
In practice, regional relevance is often tested not in grand diplomacy but in responses to concrete, time-sensitive challenges. Since early August, the ongoing detention of 18 Cambodian soldiers by Thailand has illustrated this credibility gap. More than four months after their capture, the soldiers remain in Thai custody without a transparent legal or humanitarian resolution. The issue sits squarely within the domain of humanitarian norms and post-conflict confidence-building—areas where Japan has long claimed conceptual leadership.
For decades, Tokyo has promoted “human security” as a central pillar of its foreign policy, embedding the concept deeply into its development assistance framework. As articulated in Japan’s own policy documents, human security emphasises the protection of individual dignity, freedom from violence, and recovery from conflict. Yet human security was never intended to operate only through long-term development programming. It also provides a basis for diplomatic engagement during moments of acute crisis.
In the present case, however, human security has not translated into visible diplomatic initiative. Japan has neither publicly nor quietly positioned itself as a facilitator for humanitarian resolution. This is notable not because Japan failed a moral test, but because it missed a low-risk opportunity to apply its own doctrine in practice as Japan’s comparative advantage could have been exercised. Quiet humanitarian diplomacy—behind closed doors, without public pressure—would not have challenged Thai sovereignty or disrupted ASEAN processes. It would have established a minimum level of humanitarian restraint, often a prerequisite for broader de-escalation.
Beyond norms, Japan also possesses underutilised structural influence. Thailand remains one of Japan’s most important economic partners in Southeast Asia. Japanese firms are deeply embedded in Thailand’s manufacturing and industrial base, with an estimated 5,000–6,000 Japanese companies operating across key sectors, particularly automotive, electronics, and industrial supply chains. In 2025 alone, Japanese investment in Thailand reached approximately 71.8 billion baht (around US $2 billion) in the first eight months of the year, making Japan one of Thailand’s leading sources of foreign direct investment. By contrast, Japan’s investment footprint in Cambodia is considerably smaller, underscoring the asymmetry in Tokyo’s economic leverage between the two countries.
Japan’s economic leverage also carries humanitarian implications. Thailand’s reliance on Japanese capital, technology, and long-term industrial partnerships gives Tokyo channels of influence that do not require confrontation. Even calibrated signalling—linked to stability and restraint—could contribute to limiting escalation, including the use of airpower, thereby reducing civilian harm. Such influence would be indirect and incremental, but even marginal restraint matters in preventing conflicts from widening or hardening.
Yet the humanitarian consequences of the conflict raise a more uncomfortable question about how Japan’s princeiples are applied in practice.
Japan’s so-called ‘pragmatic selectivity’ in the 2025 Cambodia–Thailand border conflict amounts to little more than a thinly veiled prioritisation of geopolitical positioning over the human cost of the crisis. While Tokyo has long positioned itself as a global champion of human security—a concept it helped popularise in the 1990s to emphasise protection from fear, want, and indignity—its response to the displacement of over 500,000 Cambodian civilians has been conspicuously muted. Many of those displaced are women, children, and the elderly fleeing artillery fire and airstrikes. Japan issued polite calls for ‘restraint’ and ‘dialogue,’ provided modest humanitarian assistance, and supported ASEAN’s tepid mediation efforts, yet it refrained from using its considerable economic and political leverage over Thailand—one of its oldest and most important regional partners—to press for de-escalation or accountability. This inaction cannot be credibly explained by appeals to ASEAN non-interference when Japan has shown greater willingness to criticise, sanction, or condition aid in other contexts where its strategic interests were more directly engaged. The result is a painful demonstration that human security remains selective in practice: universal in rhetoric, but conditional when the victims are caught in a conflict that does not directly threaten Tokyo’s sea lanes or anti-China alignment.
This selective empathy reveals a deeper and more troubling reality. Japan’s foreign policy in Southeast Asia increasingly subordinates the welfare of ordinary people to the imperatives of great-power competition with China. The appointment of China-focused ambassadors to Phnom Penh, the quiet cultivation of economic alternatives to BRI projects, and the calibrated pressure applied to Cambodia all point to a clear hierarchy of interests—one in which preserving Cambodia as a counterweight to Chinese dominance ranks higher than alleviating acute humanitarian suffering caused by a neighbouring country’s military actions. In this calculus, the lives and dignity of hundreds of thousands of displaced Cambodians become collateral damage in a broader strategy of soft balancing and counter-bandwagoning. Far from acting as a neutral, non-threatening partner that ‘respects regional norms,’ Japan appears to be adopting the same cold pragmatism it once criticised in others: promoting universal values when they align with national priorities, and quietly shelving them when they do not. This is not strategic maturity; it is moral expediency, and it risks eroding the credibility Japan has spent decades cultivating as a principled, human-centred actor in Asia.
Prolonged silence also risks undermining Japan’s own long-term investments in the Mekong subregion. Continued air operations and damage to civilian infrastructure would erode the connectivity, stability, and confidence underpinning Japan-supported economic corridors, including its long-standing Southern Economic Corridor initiatives.
Japan’s leverage also provides a pathway to reinforce international law without taking sides. By linking stability, restraint, and respect for legal mechanisms to the broader climate of economic cooperation, Tokyo can quietly encourage a return to law-based dispute management. This approach would be consistent with Japan’s long-standing advocacy for international adjudication and rules-based order.
Consistency matters beyond Southeast Asia. Japan has been a vocal supporter of international legal mechanisms, including its backing of the Philippines’ 2016 arbitration case under the Permanent Court of Arbitration, even when the ruling was politically inconvenient for China. Applying the same commitment to legal principles in the Cambodia–Thailand conflict—without adjudicating blame—would reinforce Japan’s credibility as a defender of international law as a system, not a selective instrument. At a time when Japan faces heightened tensions with China over Taiwan, demonstrating such consistency strengthens its global standing and preserves the trust that has long distinguished it in Southeast Asia.
To date, Tokyo has stopped short of articulating this legal framing in the current conflict. That restraint may reflect caution, but it also leaves Japan’s commitment to international law under-communicated at a moment when credibility matters most.
Japan has not lost Southeast Asia. But relevance is not static. It must be reaffirmed through selective engagement when stakes are high and outcomes uncertain. In the Cambodia–Thailand conflict, Tokyo chose caution. That choice avoided immediate risk—but it also ceded political space.
The lesson is not that Japan should compete with the United States or China in crisis diplomacy. It is that Japan’s comparative advantage lies precisely in doing what others do not: quiet mediation, humanitarian facilitation, disciplined economic signalling, and consistent support for international law. These tools remain available. Whether Tokyo chooses to deploy them will determine whether Japan continues to be seen as a stabilising presence—or merely a well-intentioned observer—in Southeast Asia’s increasingly contested future.
Chhay Lim is currenlty Designated Deputy Director of Center for Southeast Asian Studies, Institute for International Studies and Public Policy, Royal University of Phnom Penh.
Dr. Chandarith Neak is Associate Professor and Director of Institute for International Studies and Public Policy, Royal University of Phnom Penh.
-Khmer Times-
