Varying degrees of dependence – and interdependence – dictate how Thailand approaches its neighbors. Attention naturally fixates on adjacent states, not least because the poorly demarcated frontiers of mainland Southeast Asia are a hotspot for armed confrontation and illicit businesses. Drug trafficking, cyber scam operations, and unregulated rare earth mining are all concentrated in this sub-region.
But now is an opportune time to reflect on Thailand’s low-friction dynamics with Singapore and Indonesia, given their recent diplomatic momentum amid mounting global supply chain risks, and the Thai government’s pursuit of a more proactive foreign policy aimed at better communicating national interests.
Early this month, Thai Prime Minister Anutin Charnvirakul and Singaporean Prime Minister Lawrence Wong met in Bangkok for the fifth Thailand-Singapore Leaders’ Retreat – the highest-level forum for their bilateral engagement – after an 11-year hiatus. Both sides pledged greater cooperation on energy and food security, digital and physical connectivity, defense, and regional strategic matters as they prepare to chair the Association of Southeast Asian Nations (ASEAN) in alphabetical succession following the Philippines’ current term.
Thailand-Singapore ties, which the Singaporean premier described as being in “excellent shape,” have gained fresh vigor since the 60th anniversary of their diplomatic relations last September. The defense dimension stands out, with reciprocal visits by defense ministers and the top brass, and a study trip by a delegation from the Chulachomklao Royal Military Academy led by Princess Maha Chakri Sirindhorn, the sister of King Maha Vajiralongkorn.
The Thailand-Singapore defense partnership is indeed one of the most robust within ASEAN. First, Thailand and Singapore are probably Southeast Asia’s two most active participants in combined military exercises and maintain high-tempo, tri-service drills with each other on a bilateral level. Kocha Singa (army), Flash Thunder (special operations), and Air ThaiSing (air force) run annually. Singsiam (navy) is held biennially but is complemented by the annual Singapore-India-Thailand Maritime Exercise. The Cope Tiger aerial exercise alongside the United States is another one of Thailand and Singapore’s annual trilateral engagements. All this is without mentioning Cobra Gold, Southeast Asia’s largest multilateral all-domain exercise, held in Thailand every year.
Second, Thailand has provided the Singapore Armed Forces with dedicated training space as they face severe land constraints at home. Even with training areas elsewhere in the region, Thailand remains uniquely valuable for Singapore’s military. For one, access agreements with Thailand do not require carefully managing political sensitivities in the way those with Indonesia do. And, compared to Brunei, Thailand has more physical capacity to accommodate expansive maneuvers.
Third, despite several ASEAN members sourcing defense equipment from Singapore, only Thailand has procured high-value strategic assets, as data from the Stockholm International Peace Research Institute shows. In 2008, four years after Singapore transferred seven of its F-16A/B fighters to Thailand in exchange for 15 years of access to Thai training areas, the Royal Thai Navy (RTN) signed a $132 million order for an Endurance-class amphibious assault ship later christened as HTMS Angthong. The RTN’s only other amphibious ship today is HTMS Chang (Type-071E) obtained from China. In 2026, Singapore’s ST Engineering was among the RTN’s choices to supply its next-generation frigate, even though South Korea’s Hanwha Ocean won in the end. What this suggests is strong Thai confidence in Singapore’s defense standards and advances relative to the rest of ASEAN.
The dynamic of Thai geographic advantages and openness complementing Singapore’s value-added expertise promises broader investment in Thailand, which has traditionally been Southeast Asia’s manufacturing powerhouse and is pivoting toward advanced, high-value industries. Thailand and Singapore’s complementary strengths were highlighted when Anutin met Singaporean Defense Minister Chan Chun Sing back in April to discuss, among other things, further cooperation in aircraft maintenance, repair, and overhaul. A look at the Bank of Thailand’s record confirms that as of Q1 of 2026, Singapore alone accounts for almost 95 percent of ASEAN’s total accumulated foreign direct investment into Thailand. Singapore has in fact surpassed everyone globally, representing 25.5 percent of Thailand’s overall foreign direct investment. Japan, Thailand’s longstanding top investor, now ranks second at around 24.8 percent.
Similar to Thailand-Singapore relations, Thailand-Indonesia relations have been on an upswing since 2025. The difference is that rather than moving from strength to strength, ties between Bangkok and Jakarta have gone from underwhelming to what is expected of ASEAN’s two biggest economies. Their first-ever Leaders’ Consultation was held during Indonesian President Prabowo Subianto’s official visit to Bangkok in May 2025, just as ties were elevated to a Strategic Partnership. Anutin’s subsequent visit to Jakarta last month, ending a 15-year absence by a Thai prime minister, was trade-oriented, covering the halal supply chain, cooperation on carbon markets, and tourism. The repatriation of nearly 1,000 Indonesian nationals, who had fallen victim to transnational scam operations, was the only specific political and security issue underscored.
The prioritization of trade and investment makes good sense for Thailand, now one of ASEAN’s biggest outward investors due to a combination of factors: large corporate cash reserves, currency stability, and slow domestic growth hampered by an alarming demographic decline. Thai corporates obviously find Indonesia, one of the most populous countries on earth, attractive. Besides, Thailand has already placed capturing a larger share of the global Muslim consumer market on the national agenda, recognizing it as having massive growth potential. The National Halal Industry Committee, for instance, was established in 2024 to tap into that potential.
Yet trade and investment are the most contentious aspects as Thailand and Indonesia target the same international investors in the same industries, notably vehicle manufacturing. The narrative making the rounds in Thailand these days is that the country has to choose between retaining its status as a regional automotive hub for Japanese cars or making way for Chinese electric vehicles. So when Indonesian Finance Minister Purbaya Yudhi Sadewa openly urged Japanese carmaker Toyota to shift its production away from Thailand to Indonesia last month, he was throwing down the gauntlet.
Perhaps to a lesser extent, the push-and-pull dynamic likewise manifests in political and security cooperation. A case in point is Indonesia’s role in addressing the separatist insurgency in Thailand’s southernmost provinces, with Malaysia serving as the primary mediator. Because certain elements in the Malaysian state apparatus lend tacit support to the Malay-Muslim insurgents, Bangkok harbors the view that Kuala Lumpur is not an honest broker and has occasionally turned to Jakarta for help. The 2008 Bogor peace talks brokered by Jakarta and the 2020 intelligence-sharing pact between Thai and Indonesian armies to track fugitives are clear examples. Not only is Jakarta endowed with diplomatic credibility as the biggest Muslim-majority country, but it also has experience resolving the insurgency in Aceh. Still, involving Jakarta more explicitly could mean internationalizing the conflict, and that is not something Bangkok is prepared to handle.
In short, Thailand’s relations with both Singapore and Indonesia are positively blooming. The dynamic of dependence with Singapore is more extensive and straightforward than that with Indonesia. But substantive expansion in the case of the latter, should it materialize, could be more impactful.