Until 1990, it was illegal for transnational tobacco companies (TTCs) to sell cigarettes in Thailand. We reviewed and analysed internal tobacco industry documents relevant to the Thai market during the 1980s. TTCs’ attempts to access the Thai cigarette market during the 1980s concentrated on political lobbying, advertising and promotion of the foreign brands that were illegal to sell in Thailand at the time. They sought to take advantage of the Thai Tobacco Monopoly’s (TTM) inefficiency to propose licencing agreements and joint ventures with TTM and took advantages of unclear regulations about cigarette marketing to promote their products through advertising and sponsorship activities. After their initial efforts failed, they successfully lobbied the US to impose trade sanctions to liberalise Thailand’s market. Similar to the situation for cigarettes in the 1980s, since 2017, Philip Morris International has worked in parallel with a pro-e-cigarette group to pressure Thailand’s government to allow sales of electronic nicotine delivery systems (ENDS; including e-cigarettes and heated tobacco products), knowing the products were illegal under Thai law. Health advocates and government authorities should be aware of past TTCs’ tactics for cigarettes and anticipate that TTCs will attempt to use international trade law to force markets open for ENDS if their domestic efforts fail.