Thailand’s tilt toward China tests treaty alliance with US

For much of the past half-century, Thailand sat securely within Washington’s defence sphere, offering the US air access, participating in combined exercises and buying large quantities of American weaponry. Now, as Bangkok’s ties with China become closer, US strategists are being pushed to revisit long-held beliefs about influence, basing and even contingency planning across the western Pacific.

Thailand: from Cold War linchpin to cautious fence-sitter

On the surface, the US–Thailand alliance still appears robust. The countries have been treaty allies since the 1950s and continue to hold recurring joint activities, including Cobra Gold - the long-established exercise that brings in thousands of troops from across the region.

The relationship runs even deeper historically. Thailand, then called Siam, became the first Asian country to sign a treaty with the United States in 1833. Later, during the Vietnam War, Thai air bases served as essential platforms for US missions. In 2003, Washington formally named Bangkok a “major non-NATO ally”, a designation it shares with close partners such as Israel and Japan.

Even so, the legacy can obscure what has changed. Although the formal framework is still in place, Bangkok’s political instincts have evolved. Thai decision-makers increasingly treat the US alliance as one instrument among several, rather than the unquestioned foundation of national security policy.

"Thailand still wears the badge of a US treaty ally, but its strategic reflexes now lean noticeably toward Beijing."

This shift has unfolded over time, shaped by economic realities, internal politics and what many in the region see as inconsistent US attention to mainland South-east Asia.

Beijing fills the vacuum after Thailand’s 2014 coup

Many observers point to the period after Thailand’s 2014 military coup as a pivotal moment. The takeover triggered a freeze in significant parts of US security engagement, since American law limits military assistance to governments that come to power through force.

China responded rapidly. With Thai military leaders facing a cooler reception from Western capitals, Beijing offered a notably more welcoming diplomatic environment.

Arms deals reveal how Thailand’s balance has changed

Defence procurement figures illustrate the direction of travel:

• Between 2016 and 2022, Chinese arms sales to Thailand reached nearly $400 million, roughly double US sales in the same period.
• Beijing has supplied Thai forces with tanks, surface-to-air missiles, radars and other equipment.
• The two countries are working on delivering Thailand’s first Chinese-built submarine, a project that has raised eyebrows in Washington.

The US still conducts more advanced training with Thailand and remains a key supplier of top-tier systems. However, the expanding footprint of Chinese equipment - alongside Chinese training and support teams - gives Beijing more day-to-day leverage within segments of Thailand’s officer corps.

"As more Chinese weapons and technicians arrive, US planners worry that once-reliable Thai bases could be politically off-limits in a future crisis."

Thailand’s strategic access: a growing question for US planners

For the Pentagon, Thailand matters not only as an ally but also as strategically valuable territory. Its military facilities sit near important corridors linking the Indian Ocean, the South China Sea and the wider western Pacific.

One location stands out: U‑Tapao, on the Gulf of Thailand. In the Vietnam War era, it hosted heavy bombers and reconnaissance platforms. In current planning, it would offer a useful stopover for US forces moving between the Middle East and East Asia, or for operations connected to the Taiwan Strait.

Increasingly, analysts argue that Washington can no longer take access for granted during high-stress contingencies - particularly those in which China is directly involved.

"US officials increasingly judge that Thailand is unlikely to host American forces in a Taiwan conflict, wary of crossing Beijing."

A related assessment from the International Institute for Strategic Studies also concludes that Thailand is highly unlikely to accept US land-based missile deployments intended to offset China or North Korea. That further narrows the menu of potential regional sites as the US looks to position new conventional missile capabilities.

Intelligence and technology worries

Alongside basing questions sits a different concern: protection of sensitive information. As Thai and Chinese militaries cooperate more closely, US officials fear that classified or high-value operational details could gradually seep towards Beijing.

That anxiety contributed to Washington’s decision in 2023 not to sell Thailand the F‑35, the US armed forces’ most advanced fighter. Thai officials themselves have acknowledged that closer Thai–China links probably influenced the American refusal.

The F‑35 is not simply a jet; it functions as an airborne data node. The US typically offers it only where it is confident that technology, software and operational methods will remain protected. With Thai political and military elites engaging more frequently with Chinese counterparts, that confidence has weakened.

A slow-motion “decoupling” of interests

Policy specialists increasingly describe the direction of travel as a gradual “decoupling” of strategic interests. This is not a dramatic rupture; rather, it is a quiet divergence of priorities that steadily reduces the scope for meaningful cooperation.

Area	Traditional US–Thai alignment	Current tension or drift
Security priorities	Counterinsurgency, regional stability, maritime security	Bangkok more focused on regime stability and balancing China
Arms and tech	US as primary supplier	Growing reliance on Chinese platforms, mixed fleets
Base access	Relatively assured in crises	Far less certain in any confrontation with China
Intelligence sharing	Broad but low-profile	US caution on high-end systems and sensitive data

Nothing here constitutes a formal split. Cobra Gold continues annually. US naval vessels still visit Thai ports. Regular military-to-military contact remains.

Yet the upper limits - what Washington is prepared to provide, and what Bangkok is prepared to back - seem more constrained than in earlier years.

Washington looks east, while Thailand looks north

Some of the drift is rooted in US priorities. After the widely publicised “Pivot to Asia” announced in 2011, American strategy became more concentrated. Attention moved towards the island chain running from Japan, via Taiwan, down to the Philippines - locations widely regarded as central in any military confrontation with China.

That emphasis has left mainland South-east Asia, Thailand included, feeling secondary. US economic initiatives and assistance have been more uneven, and US domestic politics has complicated efforts to sustain long-duration development programmes.

Thailand, for its part, increasingly views its economic and political interests as intertwined with China. Beijing is Thailand’s largest trading partner and a major source of investment in infrastructure, tourism and manufacturing. Chinese tourists and capital play a visible role in Thai hotels, industrial estates and proposals for high-speed rail.

"From the Thai perspective, hedging between Washington and Beijing is not a luxury, but a survival strategy in a contested region."

Minilateral clubs keep Bangkok at the edges

US momentum has also been channelled into smaller security groupings, including:

• AUKUS (Australia, UK, US), focusing on submarines and advanced tech.
• QUAD (US, Japan, India, Australia), framed around maritime security and rules-based order.
• Tightened trilaterals with Japan and South Korea in Northeast Asia.

These formats largely sidestep mainland South-east Asia. The Philippines has secured fresh basing arrangements and heightened attention. Thailand - a treaty ally in formal terms - has not received a similar uplift.

Analysts caution that this reinforces Bangkok’s logic: if Washington is not deeply invested, then leaning too far towards the US against China may carry greater risk than benefit.

What the shift means in practice

For anyone looking for tangible implications, the following scenarios help clarify what is at stake:

Scenario 1: A Taiwan Strait crisis

If tensions around Taiwan escalated into armed conflict, US planners would need staging areas and refuelling options. In previous decades, Thai facilities would probably have featured in that planning.

Now, Bangkok would confront an extremely difficult choice: alienate Beijing or support US operations. Many experts anticipate Thailand would try to remain at arm’s length - potentially permitting humanitarian or clearly non-combat assistance, while avoiding anything that could be read as direct participation.

Scenario 2: Missile deployments in Asia

As the US introduces new conventional missiles aimed at deterring China and North Korea, it is searching for host locations in the region. Japan and the Philippines are often discussed publicly.

Thailand, by contrast, is widely viewed as an unlikely candidate. Approval would make Thai territory a focal point for retaliation risks and would place substantial strain on relations with China. That would remove what could otherwise be a centrally positioned launch area on the South-east Asian mainland.

Key terms and dynamics worth understanding

Two ideas help explain the Thailand–US–China relationship:

• Hedging: Smaller states frequently avoid an outright choice between major powers. They may seek security advantages from one side and economic gains from another, aiming to preserve flexibility rather than fully commit. Recent Thai policy closely matches this approach.
• Minilateralism: Rather than building large alliances, governments form compact, purpose-built groups such as AUKUS or the QUAD. These can move quickly, but they can also exclude regional states and create a patchwork of obligations and blind spots.

From Thailand’s standpoint, hedging can look sensible. Chinese trade and tourism support economic growth, while the US alliance still brings status, training and a distant security safety net. For Washington, however, hedging by allies injects uncertainty into crisis planning and complicates efforts to project a unified response to coercive behaviour by China.

The danger is a gradual wearing away of cooperative habits. Fewer high-end US weapons transfers, tighter limits on intelligence exchanges, and an expanding presence of Chinese-made systems in Thai units all shift the partnership towards something looser and less dependable. Nothing collapses overnight, but the assumptions once attached to the “treaty ally” label no longer reliably apply.