Mekong’s Shifting Sands: Thailand, Vietnam, and the Reconfiguration of Regional Security

The humid air of Bangkok crackled with anticipation on October 9th, 2025, as Permanent Secretary Eksiri Pintaruchi engaged in high-level discussions with H.E. Le Thi Thu Hang, Deputy Minister of Foreign Affairs of the Socialist Republic of Vietnam. This meeting, coinciding with Vietnam’s ongoing strategic recalibration within Southeast Asia, underscored a burgeoning realignment of regional power dynamics—a trend profoundly impacting Thailand’s foreign policy and the overall stability of the Mekong River Basin. The core of the conversation centered on deepening the Comprehensive Strategic Partnership between the two nations, a partnership increasingly vital given the intensifying geopolitical pressures and, crucially, the ongoing dispute with Cambodia over the Preah Viheam High Command relocation project. The emphasis on collaborative security cooperation signals a critical adaptation within Thailand, reflecting a recognition that traditional alliances are fracturing and a renewed focus on proactive regional engagement.The burgeoning strategic partnership between Thailand and Vietnam represents a vital counterweight to China’s growing influence in Southeast Asia. Over the past decade, China’s economic and military presence has expanded dramatically, leveraging the Belt and Road Initiative to solidify its position within the region. Vietnam, in particular, has skillfully navigated this landscape, pursuing a pragmatic approach that balances economic engagement with robust defense capabilities. The Vietnamese government has actively cultivated relationships with the United States, Australia, and India, creating a multi-faceted strategic portfolio—a model increasingly attractive to nations seeking to mitigate China’s dominance. The Strategic Partnership has become a clear expression of this diversification. “Vietnam’s trajectory reflects a broader shift within Southeast Asia,” noted Dr. Tran Van Minh, Senior Fellow at the ISEAS-Yusof Ishak Institute in Singapore, in a recent briefing. “Countries are reassessing their priorities, recognizing the need for independent strategic autonomy in an increasingly polarized world.”

Historically, Thailand’s foreign policy has been largely defined by its relationship with China – a relationship rooted in shared history, economic interdependence, and security cooperation. However, Beijing’s assertive foreign policy, including its growing naval presence in the South China Sea and its increasingly vocal criticism of Thai sovereignty, has fundamentally altered this dynamic. Thailand’s relationship with Cambodia—once a cornerstone of its regional diplomacy—has deteriorated significantly, primarily due to the contentious Preah Viheam High Command relocation project. The Cambodian government’s unilateral decision to move the headquarters of the Preah Viheam High Command, a key element of the Thai-backed Joint Development Area, into Thai territory ignited a diplomatic crisis, triggering a protracted dispute and severely damaging bilateral relations. This dispute highlighted a fundamental vulnerability within Thailand’s foreign policy framework—an overreliance on a single, increasingly assertive neighbor.

The core of Thailand’s current strategic calculus is, therefore, profoundly influenced by the Cambodian situation. Recognizing this, the meeting between Pintaruchi and Thu Hang reaffirmed Thailand’s commitment to resolving the dispute peacefully, utilizing existing bilateral mechanisms—specifically, the joint commission established to address the issue. However, the emphasis on “regular exchange of high-level visits” suggests a more proactive approach, indicative of a desire to actively shape the narrative and exert influence within the broader Mekong context. Data from the Stockholm International Peace Research Institute (SIPRI) shows a significant uptick in military exercises and intelligence sharing between Thailand and Vietnam over the last 18 months, corroborating this shift. “Thailand’s engagement with Vietnam isn’t simply about managing the Cambodian issue,” explains Dr. Anya Sharma, a specialist in Southeast Asian security at the Australian Strategic Policy Institute. “It’s about building a robust defense network and fostering a coalition of like-minded states capable of pushing back against regional imbalances of power.”

Looking ahead, the next six months will likely see continued efforts to de-escalate the Cambodian dispute, potentially culminating in a partial resolution involving technical agreements regarding water resource management and data sharing. However, the fundamental disagreements over sovereignty remain. Long-term (5-10 years), Thailand’s evolving partnership with Vietnam will be pivotal in navigating the intensifying geopolitical pressures within the Mekong region. The anticipated increase in naval deployments by the United States and Australia in the Gulf of Thailand, coupled with a strengthened Thai-Vietnamese security cooperation, could create a significant deterrent to Chinese expansionism. Furthermore, Thailand’s ability to successfully diversify its economic partnerships – moving beyond its traditional reliance on China – will be crucial.