The long era of absolute monarchy was brought to a sudden end on June 24, 1932, by a bloodless coup d'etat engineered by a group of civil servants and army officers with the support of army units in the Bangkok area. The action was specifically directed against ministers of the conservative royal government and not against the person of the king. Three days after the coup a military junta put into effect a provisional constitution drawn up by a young law professor, Pridi Phanomyong. Prajadhipok reluctantly accepted the new situation that had stripped him of his political power but in principle had left the prestige of the monarchy unimpaired.

The coup leaders, who were known as the "promoters," were representative of the younger generation of Western-oriented political elite that had been educated to be instruments of an absolute monarchy--an institution they now viewed as archaic and inadequate to the task of modern government. The principals in the coup identified themselves as nationalists, and none questioned the institution of the monarchy. Their numbers included the major figures in Thai politics for the next three decades. Pridi, one of the country's leading intellectuals, was the most influential civilian promoter. His chief rival among the other promoters was Phibun, or Luang Plaek Phibunsongkhram, an ambitious junior army officer who later attained the rank of field marshal. Phahon, or Phraya Phahonphonphayuhasena, the senior member of the group, represented old-line military officers dissatisfied with cuts in appropriations for the armed forces. These three exercised power as members of a cabinet, the Commissariat of the People, chosen by the National Assembly that had been summoned by the promoters soon after the coup. To assuage conservative opinion, a retired jurist, Phraya Manopakorn, was selected as prime minister.

A permanent constitution was promulgated before the end of 1932. It provided for a quasi-parliamentary regime in which executive power was vested in a unicameral legislature, the National Assembly, of which half of the members were elected by limited suffrage and half appointed by the government in power. The constitution provided that the entire legislature would be elected when half of the electorate had received four years of schooling or after ten years had elapsed, whichever came first. The National Assembly was responsible for the budget and could override a royal veto. Real power resided with the promoters, however, and was exercised with army backing through their political organization, the People's Party.

A rift soon developed within the ranks of the promoters between civilian technicians and military officers. As finance minister, Pridi proposed a radical economic plan in 1933, calling for the nationalization of natural resources. This plan was unacceptable to Manopakorn and the more conservative military members in the cabinet. The prime minister closed the National Assembly, in which Pridi had support, and ruled by decree. Accused of being a communist, Pridi fled into exile, but army officers opposing the civilian prime minister's move sc4d staged a coup in June 1933 that turned out Manopakorn, restored the National Assembly, and set up a new government headed by Phahon. With sentiment running in his favor, Pridi was permitted to return to Bangkok and was subsequently cleared of the charges against him.

In addition to factionalism within the cabinet, the government was also confronted with a serious royalist revolt in October 1933. The revolt was led by the king's cousin, Prince Boworadet, who had been defense minister during the old regime. Although the king gave no support to the prince, relations between Prajadhipok and the political leaders deteriorated thereafter.

The first parliamentary elections in the country's history were held in November 1933. Although fewer than 10 percent of the eligible voters cast their ballots, they confirmed Pridi's popularity. Pridi and his supporters in the civilian left wing of the People's Party were countered by a military faction that rallied around his rival, Phibun. In 1934 Phibun was named defense minister and proceeded to use his ministerial powers to build his political constituency within the army. Campaigning for a stronger military establishment in order to keep the country out of foreign hands, he took every opportunity to assert the superior efficiency of the military administration over the civilian bureaucracy, which looked to Pridi for leadership. Prime Minister Phahon had to maintain a precarious balance between the Pridi and Phibun factions in the government.

The civilian conservatives had been discredited during the Manopakorn regime and by the support some had given to the royalist revolt. Their loss of influence deprived the king of effective political allies in the government. In March 1935, Prajadhipok abdicated without naming a successor, charging the Phahon government with abuse of power in curtailing the royal veto. He went into retirement in Britain. His ten-year-old nephew, Ananda Mahidol (Rama VIII, 1935-46), who was attending school in Switzerland, was named king to succeed him, and a regency council, which included Pridi, was appointed to carry out those functions of the monarchy retained under the constitution. The new king did not return to his country until 1945.

Data as of September 1987