How could Thailand have Collaborated with Japan in World War 2?
Phalaphum Tokamolthum, Thailand
At first, it seems abominable that while China, Korea, and various other countries fought desperately for their right to exist, Thailand would be just about the only nation in Asia to decide to fuel the Japanese imperial war machine. Growing up in Thailand, I have heard many explanations for what kind of position Thailand was really in during the war. Several years ago, I remember how my Thai tutor was telling me an anecdote about how a group of friendly Japanese soldiers were gunned down by unknowing Thai soldiers due to miscommunication between the two nations, which were allied at the time. I had several questions, one of those being whether Thailand was on the side of the Americans or the Japanese. She kindly explained that Thailand was trying to play both sides for the nation's own survival. Ever since then, I wanted to know just a little bit more about whose side Thailand was really on, and what judgements, if any, can be made about Thailand and its role in this turbulent period of history.
In 1939, Thailand was stuck between a rock and a hard place; although recognising the danger of the expansionist Imperial Japan, Thailand had a deep-rooted distrust of the Allied Britain and France. From the 18th to the 20th century, France and Britain colonised large parts of Thailand and its neighbors and had systematically undermined its economic sovereignty, as is the nature of colonialism. The expansion of British Burma, French Indochina, and Britain’s acquisition of territories in Malaysia surrounded Thailand with less-than-friendly neighbors. The losses of Thailand are seen through a timeline of signed treaties. In 1855, the signing of the Bowring Treaty undermined Thai economic sovereignty to British money, with terms agreeing to allow greater English trade and ownership of land within Thailand (Bowring, 1856). In 1893, 1904, and 1907, Thailand signed three treaties relinquishing lands to its east, which are now modern-day Laos and Cambodia, to French Indochina. Finally, in 1909, Thailand signed another treaty with Britain, ceding Kelantan, Terengganu, Kedah and Perlis to Britain in Malaysia. (Brady and Thibault)
What is also to be considered, coming from this sort of history and in the wake of fascist movements in the early 20th century, is the Thai leader at the time, Plaek Phibunsongkram. He was heavily fascinated by the ideas of figures like Mussolini, who shaped his ideas around strong nationalism. He promoted Thai nationality over others throughout former Siam, renaming the country as Thailand and enforcing the Thai language on the many different ethnicities throughout Siam. Phibunsongkram wanted to do whatever it took to strengthen Thai nationality and culture throughout the region. (Ernst)
Whilst Britain and France colonised the world, there was another rising power in the east, one which, perhaps to Thailand, represented some sort of alternative to the old ways of colonialism. Japan, in regard to dealing with colonialism, was somewhat similar; to survive, both nations turned to industrialisation and westernising their government and military in order to keep up with the approaching colonial powers; these policies were pushed heavily from colonial times to recent history. Ultranationalists in the respective countries had tried to go even further, leading to many cases of political violence in both countries; for example, the assassination of liberal prime minister Hara Takashi in 1921 (Filippov, 2022) and the Siamese revolution in 1932. However, Japan exceeded Thailand in building its own empire with several key victories in Taiwan, China, Korea, and most importantly, Russia, proving Japan’s capability of standing up to European powers. Therefore, perhaps in the case of the nationalist government of Plaek Phibunsongkram, the Allies were seen at the very least as no better than the Japanese.
This is why, throughout World War 2, Thailand attacked French and British assets whether they were formally allied with Japan or not. The short and unknown Franco-Thai War from October 1940 to January 1941 was fought to reclaim the Siamese territories lost to French colonialism, all while maintaining their position to be neutral in the war (Horvath, 1995). In December 1941, Thailand officially allied with Japan, allowing Japan access to Thai territory for military use. During its alliance with Japan, Thailand would contribute to aiding military campaigns in Burma, Malaysia, and Indonesia, with aims to reclaim historical Siamese lands in Laos and Cambodia. (Diwik, 2019)
One especially insidious case of Thai-Japanese collaboration would be in the building of the Burma Railway. Starting in 1940 and finishing in 1943, the construction of the Burma Railway would heavily utilise forced labour from conscripts and prisoners of war (POW) mainly hailing from the British Commonwealth nations, the Netherlands and America. The conditions under which the labourers built the railway were grim. In transport from the front lines, they were packed tightly into “death ships”, with a death rate of 1 in 5 people. Once they arrived at their site of work, they were subjected to long hours and fed meager portions of boiled rice as well as spoiled meats and fish. The wet and tropical environment in which these prisoners worked cultivated diseases such as dysentery and malaria. The final death toll, including all of the conscripted civilian labour and the POWs, can be estimated to be over 100,000 approximately, with a casualty rate of over 10% for most groups. The important fact to keep in mind here is that the construction of the railway was agreed upon by Thailand with the Japanese, making Thailand complicit in these atrocities. (Bowden, 2025)
Plaek Phibunsongkram was not formally trialed or charged for any of his actions during the war. The international community, with the exception of Britain, did not wish to punish Thailand for its collaboration with Japan during the war. Near the end of the war, a coup set by the Free Thai movement, funded by Allied intelligence, against Plaek Phibunsongkram was able to turn Thai forces towards the Allies and marginally contributed to campaigns against Japan. As the Cold War and the rise of international Communism loomed over the heads of first world leaders, America would push towards supporting Thailand as a strong ally in Southeast Asia rather than putting Thailand on trial. (Keyes, 2025) (Baker & Phongpaichit, 2022)
This is perhaps an inevitability of the Cold War, as Japan and West Germany too would be supported and aided against Communism.
But how should we see these actions that Thailand took during the war? Could the claim that Thailand was acting in its best interests really justify its collaboration with Japan? There are some things to consider. Japan in the war was indeed a much stronger power than Thailand; I believe that in most hypothetical engagements, Thailand at the time would quickly be taken over, losing its sovereignty. This is likely, as Japan had been able to do the same throughout the rest of Asia. At the time, Japan really was making staggering progress in conquering East Asia; regions such as Korea, mainland China, Formosa (today known as Taiwan), and other European Colonies were quickly defeated in Japan’s war of conquest. Could we really expect Thailand alone to fight Japan and maintain its sovereignty? From this perspective, we can see why Thai leaders decided to collaborate.
But we should not forget the weight of Thailand’s decision in the war. In collaborating with Japan, Thailand signed off on its air bases and naval ports to be used by Japan, and after all, it was Thailand's decision to collaborate that allowed Japan to carry out its war crimes in building the Burma Railway and to carry out its campaign throughout Southeast Asia. Civilian lives throughout places like Indonesia and the Philippines were destroyed by the Japanese planes and ships departing from Thailand. While we should know the historical context which informed collaboration, we should also be aware of its historical consequences.
This topic remains with the leaders of the world to this day: how can we be sure that we’re on the right side of history? And how do we contend with the fact that sometimes, choosing to be on the side that aligns with our morals could cost us dearly? These questions weigh on our shoulders when we decide who to vote for (if we do decide to vote at all), what brands and companies we choose to support, and the topics we choose to speak about. This is why geopolitics is so important if we want to analyse the actions of our governments and the positions they choose to take on the world stage.
Bibliography
Baker, Chris, and Pasuk Phongpaichit. “Chapter 6 - The American era and development, 1940s to 1960s.” A History of Thailand, Cambridge University Press, 2022, pp. 155 - 186, https://www.cambridge.org/core/books/abs/history-of-thailand/american-era-and-development-1940s-to-1960s/640C809663A3C57FAAACF02E6878D9C4#chapter.
Bowden, Tim. “Prisoners and labourers on the Burma-Thailand Railway in World War II.” Anzac Portal, 12 December 2025, https://anzacportal.dva.gov.au/wars-and-missions/ww2/pows/burma-thailand-railway/prisoners#3. Accessed 5 January 2026.
Bowring, John. Treaty of Friendship and Commerce between Great Britain and Siam. 1855. Wikisource, https://en.wikisource.org/wiki/Treaty_of_friendship_and_commerce_between_Great_Britain_and_Siam/Treaty.
Brady, Cole, and Alex Thibault. “Siam Independence.”
Diwik, Ally. “An Overview of Thailand's Participation in WW2.” pacificatrocities.org, 28 June 2019, https://www.pacificatrocities.org/blog/an-overview-of-thailands-participation-in-ww2.
Ernst, Gabriel. “Euro-Fascism with Thai Characteristics.” Din Deng, 2021. https://dindeng.com/, https://dindeng.com/euro-fascism-with-thai-characteristics/.
Filippov, Dmitry. “Before Abe: A Brief History of Political Assassinations in Japan.” The Diplomat, 19 July 2022, https://thediplomat.com/2022/07/before-abe-a-brief-history-of-political-assassinations-in-japan/. Accessed 5 January 2026.
Horvath, George. “Thailand's War With Vichy France.” History Today, 3 March 1995, https://www.historytoday.com/archive/thailands-war-vichy-france.
Keyes, Charles F. “Thailand - Postwar Crisis, Phibunsongkhram, Democracy.” Britannica, 31 December 2025, https://www.britannica.com/place/Thailand/The-postwar-crisis-and-the-return-of-Phibunsongkhram. Accessed 5 January 2026.
Ray, Michael. “Burma Railway | History, Route, & Deaths.” Britannica, https://www.britannica.com/topic/Burma-Railway. Accessed 5 January 2026.
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