Constitutional government in Thailand has been hindered by traditional public apathy, and political parties generally have been formed by military personalities rather than around political issues and programs. Military leader Phibul Songgram, who became prime minister in 1938, did not favor political parties. Phibul's immediate postwar successor, the pro-Japanese Pridi Banomyong, encouraged the growth of parties, but these were generally ineffective, primarily because of Thai inexperience with such institutions.
Upon Phibul and other military leaders' return to power in 1947, parties were banned. In a move designed to undercut a growing threat from other soldiers, Phibul reinstated political parties in 1955 in preparation of the elections for 1957. A new coup, led by Marshal Sarit Thanarat, deposed Phibul in 1957 and again banned political parties. Following the promulgation of a new constitution in June 1968, parties were again legalized and hotly contested the 1969 parliamentary elections. Prime Minister Thanom Kittikachorn's United Thai People's Party won a plurality (76) of the 219 seats in the House of Representatives, giving it a majority in partnership with 72 "independents" supported by Deputy Premier (and army chief) Praphas Charusathien. The Democrat Party, led by civilian politician Seni Pramoj, won 56 seats, becoming the chief opposition party. Following Marshal Thanom's 1971 coup, political activity again subsided in favor of the military. The collapse of military rule in October 1973 led to a resurgence of civilian political groups. In the parliamentary elections of 26 January 1975, 2,193 candidates from 42 political parties contested 269 seats in the House of Representatives. Voter apathy remained a problem, however, as only 47% of the electorate (33% in Bangkok) took part. The conservative Bangkok-based Democrat Party emerged with a meager plurality of 72 seats, thereby failing to secure a majority coalition. On 13 March, Kukrit Pramoj, leader of the Social Action Party (SAP), which held 18 seats, was elected prime minister in a controversial vote; he formed a ruling right-wing coalition with the Social Justice Party (45 seats), the Chart Thai (28 seats), and four smaller groups. The coalition collapsed in January 1975, and in new elections held on 4 April, Seni Pramoj gained the premiership.
In the bloodless military coup of 23 February 1991 by the National Peacekeeping Council (NPKC), General Chatichai's government was turned out. The NPKC promulgated a provisional constitution, and after a brief period paved the way for a civilian interim government headed by Anand Panyarachun. A general election was held 22 March 1992, with 15 parties contesting 360 seats with 2,185 candidates. Persistent vote buying marred an election in which 59.2% of the electorate voted. Results were: Samakkhi Tham (79), Chart Thai (74), New Aspiration Party (72), DP (44), and Palang Dharma (41). A coalition government controlling 195 seats in the House of Representatives was comprised of Samakkhi Tham, Chart Thai, Pratchakorn Thai, the SAP and Rassadorn parties. Narong Wongman was proposed as prime minister until the United States made allegations of Narong's involvement in illegal drug trafficking. In April 1992, General Suchinda was named prime minister. His appointment as an unelected prime minister met with immediate protest. Agreement was reached to amend the constitution to prevent an unelected prime minister, but an apparent change of mind by the government resulted in violent rioting. Suchinda resigned and constitutional amendments were approved by parliament on 10 June. The National Democratic Front, four parties that had opposed the military government, the DP, the New Aspiration Party, Palang Dharma, and Ekkaparb, formed an alliance to contest the elections called for in September 1992.In the wake of the 1976 coup, massive arrests were made of liberal and leftist political elements; political parties were banned, and martial law instituted. Political activity was restored and martial rule partially relaxed under the 1978 constitution. Subsequent elections, held on 22 April 1979, gave no party a clear majority. The SAP won a plurality of 82 seats, and the Thai Nation Party finished second with 38. Gen. Prem Tinsulanonda, who became prime minister in March 1980, formed a new coalition government after the April 1983 elections, in which the SAP emerged with a plurality of 92 seats. Several days after the elections, the Thai Nation Party, which had won 73 seats, subsumed the Siam Democratic Party, which controlled 18. In subsequent elections on 27 July 1986, the Bangkok-based Democrat Party improved its position greatly, winning 100 seats. The Thai Nation Party won 63, and the SAP, 51. These three parties, along with the small Rassadorn—or People's—Party which won 18 seats, formed a new coalition, but with Gen. Prem again as prime minister. The election campaign and balloting were marred by scattered incidents of violence.
In the 13 September 1992 general election 12 parties contested 360 seats in the House of Representatives. Voter turnout was 62.1%. Election results were: the DP (79), Chart Thai (77), Chart Pattana (60), New Aspiration Party (51), and SAP (22). The DP formed a coalition party with Palang Dharma (47 seats) and Ekkaparb (Solidarity) for control of 185 of the 360 seats. The SAP was invited to join the coalition. The leader of the DP, Chuan Leekpai, was named prime minister. Chuan served for two years—the longest continuous civilian rule in modern times— before scandal brought his government down in May 1995. Elections were held in July 1995 which were won by Chart Thai, taking 92 of the expanded body's 391 seats. Chuan's Democratic Party was next with 86 seats; the NAP took 57 and Phalang Dharma slipped from 47 to 23 seats. Banharn Silpa-archa was appointed prime minister, and was almost immediately assailed by the press—and even the king—for assembling a government of largely discredited cronies.
Banharn's coalition lasted barely 14 months and new elections were held in November 1996, the results of which were as follows: NAP, 125 seats; Democratic Party, 123; Chart Pattana, 52; Chart Thai, 39; SAP, 20; Prachakorn Thai Party, 18; Solidarity Party, 8; Seritham Party, 4; Muan Chan Party, 2; Phalang Dharma, 1; Thai Party, 1. Chavalit Yongchaiyudh became prime minister in January 1997. He resigned in November, and Chuan Leekpai once again formed a coaltion government including his Democratic Party, Chart Thai, the SAP, Ekkaparb, the Sirtham Party, Palang Dharma, the Thai Party, and a majority of the Prachakorn Thai Party. Constitutional changes, promulgated on 11 October 1997 increased party discipline and loyalty. It requires representatives to resign their seat if they switch or renounce their party affiliations.
General elections were held on 6 January 2001, which were won by the new Thai Rak Thai ("Thais Love Thais") Party, led by Thaksin Shinawatra, who became prime minister. Thaksin, a multi-millionaire telecommunications tycoon, took almost twice as many seats as his rivals, but fell short of an outright majority. Thai Rak Thai took 248 of 500 seats in the House of Representatives, and the Democratic Party of outgoing Prime Minister Chuan Leekpai won 128 seats. Thaksin's coaltion included the New Aspiration Party and the Chart Thai Party. The elections were marrred by allegations of fraud and vote-buying. The results of 62 constituencies were thrown out because of voting irregularities, more than half of the disqualifications earned by candidates from Thai Rak Thai. Those constituencies held re-elections on 29 January. Thaksin was indicted by the National Counter Corruption Commission (NCCC) in December 2000 for failing to report some of his wealth. In August 2001, the Thai constitutional court voted 8–7 to acquit Thaksin of assets concealment.