The other Cambodia border issue ASEAN can’t fix

The bloody border conflict between Thailand and Cambodia this year took place a long way from Vietnam, but the implications for Hanoi are not so distant. Outwardly, Vietnam offered a modest expression of concern and call for restraint, even as the clash took lives and compelled external mediation. Vietnam’s choice not to get involved in its western neighbours’ quarrel was perhaps for the better.

Vietnam and Cambodia have their own border woes – demarcation has stalled at 84% since March 2018. But Vietnam has limited options to resolve the issue conclusively. Under Vietnam’s “four-no’s” policy, force or threat of force is not something Hanoi can entertain. Hanoi knows too well the grievous costs of military manoeuvres, having felt the massive bloodletting exacted by the spirited regional opposition to its intervention in Khmer Rouge’s Cambodia. This regional response, later recalled as ASEAN’s most credible diplomatic success, would continue to be reminisced about as a sobering and sore reminder of a grim episode not long ago.

Since Vietnam’s socialisation into the ASEAN Way and developmental dream, Hanoi has faithfully heeded the virtues of non-interference to focus on internal affairs and cultivate an external environment conducive to growth. To that end, Vietnam-Cambodia relations have seen bouts of border tensions, but none has metastasised into full-blown conflicts like the Preah Vihear temple disputes between Cambodia and Thailand.

Vietnam’s self-rehabilitation from the Cold War label of “regional hegemon” to “friend to all, enemy to none” has been successful internationally, but less so in Cambodia. To be sure, Vietnam and Cambodia maintain constructive military relationships to watch their restive border regions and guard against “hostile forces”. But this relationship has limits – it was pointed out before that Vietnam turned down Cambodia’s request for military assistance during the Preah Vihear temple crisis. Ironically, Vietnam’s faithful non-intervention then also cemented a view that Cambodia cannot rely on its large neighbour.

Compounding this perception is ASEAN’s inability to meaningfully assist Cambodia’s border woes. Vietnam was the strongest supporter of Cambodia’s accession to ASEAN even when other members did not share its enthusiasm, especially after Hun Sen’s political takeover in 1997. Hanoi may have hoped that a productive relationship with ASEAN would have also domesticated and integrated Cambodia, like it did with Vietnam after the meltdown of the socialist bloc it depended on.

That has not panned out too well. Analysts are familiar with the 2012 “Phnom Penh fiasco” with an obstructionist Cambodia, but ASEAN also offered only limited assistance in the preceding Preah Vihear temple crisis of 2008–11. Phnom Penh found little comfort in ASEAN’s onerous consultation and dispute settlement mechanisms. Then, as now, Cambodia has found more use in internationalising the conflict by going to the UN Security Council and International Court of Justice. The recent ceasefire mediated by Malaysia’s chairmanship of ASEAN was also preceded by Chinese and American outreach.

Both Hanoi and Phnom Penh have managed to keep border tensions at bay, but there is no guarantee this will last. As I’ve argued elsewhere, the appreciation for well-managed ties with Vietnam of Hun Sen and his clique may not be passed onto the new generation of Cambodia’s ruling elites, who have little memory of the war that propelled their forefathers to politics. This can be a boon for Hun Manet – Hun Sen’s intimate ties with Vietnam have been used by dissidents and opposition politicians to delegitimise him as “Hanoi’s puppet”. Moves such as the Funan Techo Canal project and withdrawal from the Cambodia–Laos–Vietnam Development Triangle Area could be interpreted as an effort to wean off Vietnam under Hun Manet, detaching himself from the label that his father struggled with his whole political career. As Hun Sen ages, so does Vietnam’s influence in Cambodia.

Such relationships cannot always outmanoeuvre, let alone outlast, the historically entrenched worldview of a Cambodia preyed upon by the “Thai tiger” and “Vietnamese crocodile”. On this, there is some sense that the crocodile is more fearsome. Given shared Hinduized Theravada Buddhist cultures, ruling families’ ties, and constitutional monarchic regimes, the Cambodia-Thailand tussle can be portrayed as a civilisational competition between cultural kins. With its different traditions and demonstrated military might, communist Vietnam represents a less knowable, racialised and “hereditary enemy” outside this Theravada Buddhist family. Anti-Vietnam sentiment permeates Cambodian society, informs nationalist conspiracy theories, and throttles Hanoi’s efforts to promote understanding, save for more formal, limited instances of personnel exchange and scholarship programs.

Shorn of ideological and military leverage, Vietnam may only have economic tools to augment its influence in the region. Even this pales in comparison to China and, importantly, it may only hold for Laos. Continued economic prosperity could improve Vietnam’s standing in the region, but it could also inflame Cambodia’s anxieties of a resurgent Vietnam.

Such speculation may seem far-fetched, but not so unreasonable when viewed along the lessons Vietnam learned in decades not so long gone. As public views of Cambodia sour in Vietnam, Hanoi has shown diplomatic adroitness with major global powers, yet remains in a bind when it comes to its southwestern neighbour.

By Minh Son Ton – The Interpreter / Lowyinstitute.org – 14 octobre 2025