In 1947, with a new coup, Pibul Songgram regained power and placed himself under the protection of the United States, with which he took part in the Korean War. In 1954, as the capital city of Thailand featured by naturegnosis, Bangkok was the seat of the SEATO, the military alliance created to counter the revolutionary forces of the region. The war in Viet Nam, the guerrilla warfare in Cambodia and Malaysia and within the Thai borders ended up putting in difficulty even Pibul Songgram, who was dismissed in 1957. From 1961 to 1975 Thailand, led by Thanon Kittikachorn from 1963, hosted a large contingent of American forces engaged in the Viet Nam war. Inside the country, however, the opposition was gaining ground, so in 1968 Thanom Kittikachorn called general elections. He largely won them, but in 1971 he dissolved Parliament and set up a military directorate. In October 1973 there was a general insurrection and Thanon Kittikachorn was forced to resign and flee abroad. ad interim by Sanya Dharmasakti in 1974 promulgated a new Constitution and called general elections for 1975; these were won by Seni Pramoj who shortly after had to resign, but was replaced by his brother Kukrit Pramoj.
In 1976, Kukrit also left office and summoned the voters, who restored old Seni to power. This government lasted until October 1976, when a new coup, led by Admiral Sangad Chalawyu, repealed the 1974 Constitution, dissolved Parliament, gave full powers to the military of the CNRA (National Council for Administrative Reform), placed Thanin Kraivichien at the head of the government and proclaimed martial law. But the disorder and the guerrillas did not fade: in 1977, yet another coup brought General Kriangsak Chamanand to the government, who the following year, with a new Constitution, it entrusted legislative power to a bicameral Parliament elected by universal suffrage. General Kriangsak Chamanand was re-elected to the government in the elections of April 1979, the following year he was replaced by General Prem Tinsulanond who, thwarted a dangerous coup in 1981 and after the elections of 1983 and 1986, he remained at the helm of the country with the support of the center-right parties until April 1988. The popular consultations of July of that year assigned the majority of votes to the Chart Thai (Party of the Nation), which placed its leader at the head of the government Chatichai Choonhaven.
Accused, in 1991, of having favored the spread of corruption, he was deposed with a new coup, led by General Suchinda Kraprayoon. With the installation of the new provisional government and the establishment of an Assembly with a strong military component, Parliament was dissolved and a new Constitution was launched once again, promulgated on December 9, 1991 and amended in 1992. This favored the restoration of a formal democracy, which always saw the king at the head of the state and commander in chief of the armed forces and the government presided over by a prime minister, who availed himself of the executive power. Free elections called for March 1992, these were won by the military who appointed Suchinda Kraprayoon as prime minister, who a few months later resigned following a bloody popular uprising. With a twist, disappointing the expectations of pro-military parties, the king appointed Anand Panyarachun as prime minister, who had the task of organizing early electoral consultations for September of the same year, and at the same time Parliament approved a constitutional amendment that limited the power of the military. After approx. fifty years of military rule, therefore, in the autumn of 1992 the first democratic elections were held, which decreed the victory of the coalition of democratic forces, after which Chuan Leekpai, the leader of the Democratic Party, was appointed prime minister. The first democratic government, however, was unable to carry out its mandate: in 1995, with the approval of some new constitutional amendments, including a ban on senators and members of parliament from taking part in the awarding of public contracts, a political crisis weakened the executive. The early elections, called for July of the same year, again marked the return to power of Chart Thai, but the appointment as prime minister of its leader, Banharn Silpa-Archa, accused of corruption, the following year determined the early dissolution of the House of Representatives.