ហេតុអ្វីបានជាគោលនយោបាយការបរទេសមិនចូលបក្សសម្ព័ន្ធរបស់វៀតណាមតម្រូវឱ្យមានកិច្ចសហប្រតិបត្តិការពីប្រទេសថៃ?

Mainland Southeast Asia’s strategic equilibrium ultimately rests on the mutually reinforcing foreign policy approaches of Hanoi and Bangkok.

Vietnam’s “Four Nos” doctrine – which commits it to no military alliances, no siding with one country against another, no foreign military bases on Vietnamese soil, and no use of force or threat of use of force in international relations – is often interpreted as the backbone of the country’s policy of non-alignment in the current phase of intensifying great power competition. However, the recent Cambodia-Thailand border conflict reveals a no less important aspect of the policy, which is that Hanoi also seeks to be non-aligned with regard to disputes among its peer neighbors, except for Vietnam’s sole treaty ally Laos. This is a huge policy reversal compared to the heyday of the Third Indochina War (1977-1991), when Hanoi backed the People’s Republic of Kampuchea in its border clash with Thailand, partially resulting in Vietnam being internationally isolated and economically bankrupted.

Vietnam’s goal since the 1991 Paris Peace Agreements on Cambodia has thus been to avoid the polarization that had plagued Indochina between 1977 and 1991, and led directly to its dual-front war with the Khmer Rouge and China. Vietnam wants to deny the great powers any pretext for military interference in the contemporary Cambodia-Thailand border disputes, along the lines of the Sino-Soviet split during the Third Indochina War.

Throughout the Cambodia-Thailand border conflict, Vietnam has adhered to its Four Nos as the principle for mediating between Bangkok and Phnom Penh. Vietnam called for a renunciation of the use of force and a peaceful resolution of the conflict by dialogue in accordance with international laws and regional agreements. It has emphasized the ASEAN Charter and “ASEAN centrality” as the basis for conflict resolution, and it did not show support for either Thailand’s preferred bilateral approach to resolving the conflict or Cambodia’s preference for the internationalization of the border dispute. In short, Vietnam did not side with one country against another.

Vietnam’s non-aligned foreign policy has helped to address external and internal security threats from Thailand and Cambodia. In December, when discussing the Cambodia-Thailand border clash, Vietnam and Thailand affirmed that they would tighten security cooperation and pledge not to let any individuals or organizations use their territory as a base to attack the other. Thailand’s commitment includes its withdrawal of support for anti-Hanoi organizations stationed in Thailand. In the past, these organizations, based in Thailand were seen to pose a danger to Vietnam’s communist government either by threat of violence or by propaganda.

Thailand’s recent extradition to Vietnam of Y Quynh Bdap, whom the Vietnamese government claimed to be the mastermind behind the June 2023 terror attack in Vietnam’s Dak Lak Province, is a case in point. By committing not to support Cambodia militarily under its Four Nos policy, Hanoi in exchange got Bangkok to commit to quash threats to its internal security. Not supporting Cambodia like Hanoi did in the 1970s and the 1980s, or even as far back as in the 1840s during the days of the Nguyen dynasty, also prevents the border conflict from triggering a great power intervention and reviving the traditional Thai external security threat to Vietnam.

Vietnam has also shown Cambodia the limits of its relationship with China. In recent years, Cambodia has spoken with confidence of its ability to escape Vietnam’s orbit thanks to growing Chinese support. In 2024, Phnom Penh pushed forward with the construction of the Funan Techo Canal and withdrew from the decades-old Cambodia-Laos-Vietnam Development Triangle Area agreement despite Vietnam’s discontent about both decisions.

However, as the border clashes show, Chinese backing was not enough to deter Thailand from launching attacks against Cambodia-held positions, and Chinese arms proved to be insufficient to defend Cambodia from the superior Thai firepower. By withholding military support for Cambodia, Hanoi has demonstrated to Phnom Penh that it cannot defend itself against Thailand, because China cannot attack Thailand to relieve pressure on Cambodia like Beijing did to Vietnam in 1979. Phnom Penh’s loss of small pieces of territory is not damaging enough to China’s core interests to warrant a Chinese troop deployment to Cambodia. It is thus in Vietnam’s interest to keep the conflict limited and Cambodia aware of its material weakness so that it will no longer bet solely on Chinese support. A Cambodia less reliant on China is less likely to pose a threat to Vietnam’s southwestern provinces.

However, Vietnam’s non-alignment policy cannot succeed in stabilizing mainland Southeast Asia if either Cambodia or Thailand fails to eschew great power interference in regional affairs. Vietnam’s limited agency means that it cannot avoid being entangled in regional polarization if either China or the United States establishes a military footprint in mainland Southeast Asia, in response to the Cambodia-Thailand conflict or for any other reason. In this instance, China and the United States, like China and the Soviet Union in an earlier era, would exert massive pressure on Hanoi to pick a side so that they can gain an edge in the regional military balance. As such, Vietnam, Thailand, and Cambodia must cooperate to tighten their respective non-aligned foreign policies. Vietnam wants its neighbors to adhere to their own versions of the Four Nos, which is that both Thailand and Cambodia should not host foreign military bases and continue adhering to ASEAN conflict resolution mechanisms instead of seeking great power backing.

Counting on Cambodia might prove difficult. As much as Cambodia may now have diversified foreign relations and share a preference for non-alignment, recourse to great power protection remains a constant due to a combination of factors: the country’s material limitations, its enduring perception of its more powerful immediate neighbors as existential threats, and path-dependent strategic practices across leaderships. If the French accounts are accurate, Cambodian King Ang Doung proactively sought France’s protection from Siam and Annam in 1853, 10 years before the protectorate was established under King Norodom, when French contacts with Cambodia were still indirect and cautious. Prince Norodom Sihanouk tilted toward China despite institutionalizing non-alignment in post-independence Cambodia. The Khmer Rouge also counted on Chinese regional interference to deter a Vietnamese counterattack as it escalated its border war with Vietnam  in the mid-1970s. Post-Cold War Cambodia enshrined non-alignment in its constitution, but it leaves open the possibility of external assistance for self-defense.

Even when its survival was not objectively under imminent threat, Cambodia has still bet on great power assistance. The more localized Cambodia-Thailand border confrontations of the 21st century are a case in point. This conflict is different from the Cold War confrontations because, beyond the normative or reputational constraints that prevent the materially stronger Thailand from mounting an extensive military and economic offensive against Cambodia, great power involvement is not a built-in feature but rather contingent upon deliberate invitation. There are currently no great power military footprints in continental Southeast Asia. The 2008-2011 Cambodia-Thailand border clashes catalyzed the Hun Sen regime’s rapid tilt toward China, as famously manifested in Cambodia’s unprecedented veto as ASEAN chair in 2012 of a joint communiqué critical of Chinese actions in the South China Sea. Cambodia has also reportedly granted China exclusive access to parts of its Ream Naval Base.

The more violent and extensive 2025 border clashes saw the Hun Manet government calling on Chinese President Xi Jinping and U.S. President Donald Trump, among other world leaders, to be more involved in enforcing the border ceasefire. However diplomatically and politically framed, and however understandable for Cambodia as the smaller party, such an invitation inherently left the door wider open for the establishment of a military footprint by external powers and undermined the principle of ASEAN centrality. Great power oversight has the potential to incentivize Thailand and Cambodia to posture for outside audiences and neglect the gradual technical solutions required for long-term border management. It can also elevate the Cambodia-Thailand border conflict into an arena for the United States and China to showcase their different visions for regional order, especially over issues such as sovereignty or conflict resolution mechanisms.

The ruling Hun family will have to strike a difficult balance between the United States and China so as to win both of their support for its internationalization of the border conflict. Regardless, Cambodia has a tendency to bring in external powers in localized affairs, even when their presence may escalate Cambodia’s disputes with its neighbors. Accordingly, Cambodia’s decision to rely on external support might push Thailand to side with another great power to balance against Cambodia’s external backer, a phenomenon commonly referred to as the alliance security dilemma. Thailand’s alliance policy is something that Vietnam alone cannot dictate, but any change in it would have major repercussions for Hanoi’s own non-alignment.

Thailand’s foreign policy, which has stood the test of time, is popularly known as “bamboo diplomacy,” or more recently, “complex engagement.” The unchanged core is engaging multiple powers to varying degrees depending on specific issues and accommodating their interests without fundamentally surrendering the country’s strategic autonomy. However, the basis of this policy depends on Thailand feeling safe enough to not have to rely on any great power. During the Cold War, Thailand had to ally with the United States and later China to counter a Soviet-backed Vietnam. It was the withdrawal of the great power presence from Indochina at the end of the Cold War that has allowed Thailand to practice its non-alignment policy.

Thailand today remains a U.S. treaty ally, as highlighted by last month’s Cobra Gold drill and grand opening of a new “state-of-the-art” U.S. consulate in the northern Thai city of Chiang Mai. Yet when it comes to basing rights, perhaps the most consequential aspect of a security alliance, Thailand has repeatedly turned down U.S. advances, all while steadily expanding defense relations with other nations. China, which has neither a direct land border nor any territorial dispute with Thailand, is one such partner. Newer arrangements have been pursued cautiously to reassure traditional Western partners. In the China-Thailand Falcon Strike air exercise, for instance, the Thai side has agreed not to deploy American F-16s and has operated Swedish Gripens with selected features disabled.

So while Thailand may not articulate a doctrinal Four Nos policy like Vietnam does, its behavior as an avid hedger matters in stabilizing regional non-alignment. First, as one of the founding ASEAN members, Thailand’s hedging helps underpin the concept of ASEAN centrality as a principal non-aligned platform for regional interactions. Sure enough, ASEAN has faced relentless criticism for failing to deal with intra-ASEAN disputes. Even so, ASEAN centrality remains valuable as the normative justification against unwanted external involvement.

Second, Thailand’s geostrategic value would make any firm Thai alignment alarming to regional states, at least psychologically, in turn undermining the resolve to sustain non-alignment. Whichever great power dominates Thailand is seen as gaining access to the Southeast Asian hinterland along with maritime theaters in the Gulf of Thailand and the Andaman Sea. For instance, Thailand was a key corridor to the Japanese wartime expansion into Burma and Malaya. Thailand is also logistically ready for military – particularly air – operations. Vietnam understands this more than anyone, as the majority of the U.S. bombing missions against North Vietnam, Laos, and Cambodia in the 1960s and early 1970s were launched from Thailand. Thailand’s alliance posture directly impacts Vietnam’s foreign policy, past and present.

Should Thailand side overtly with a great power against Cambodia in the context of the current border tensions, it would be driven less by prudence than by a security dilemma. Not only is the conflict regarded by Thailand as non-existential and something that should be contained as bilaterally as possible, but the polarization of the global order makes calibrated hedging more valuable than ever. Vietnam decision to maintain its neutrality in the Thai-Cambodian conflict is likely to produce crisis-dampening effects, as Hanoi is neither encouraging Cambodia to double down on external backing nor encouraging Thai impulses for counter-alignment. Besides, Hanoi’s neutrality as a mainland Southeast Asian nation historically involved in Thai-Cambodian affairs will discourage other more distant ASEAN nations from taking sides. Ultimately, Thailand should feel safe enough to maintain its non-alignment posture, which in turn strengthens Hanoi’s Four Nos.

With Cambodia and Laos structurally dependent on external support, and with Myanmar constrained by lasting internal turmoil, mainland Southeast Asia’s hedging equilibrium ultimately hinges on the reinforcing foreign policy approaches of Vietnam and Thailand. If the Cold War provides any clues, it is that when either Bangkok or Hanoi sides with a great power, the other shortly follows suit. An ASEAN-centric solution to the Thai-Cambodia conflict may have limits, but it remains the region’s best hedge against regional polarization and great power interference.

thediplomat