General elections were held in Thailand on 6 February 2005. The result was a landslide victory for the Thai Rak Thai party of Prime Minister Thaksin Shinawatra, which won 377 of the 500 seats in the House of Representatives, with its former coalition partner, the Chart Thai Party taking 25 seats. The opposition Democrat Party of Thailand won only 96 seats and the newly formed Mahachon Party took two seats.

Following the 2001 general elections, the New Aspiration Party merged into Thai Rak Thai, although it was later re-established by Chingchai Mongkoltham. The National Development Party (Thailand) and Seritham Party also merged with Thai Rak Thai Party.

At the time of the elections the House of Representatives consisted of 400 members elected from single-member constituencies and 100 members elected from national party lists on a proportional basis.

The Democrat Party led by Banyat Bantadtan did not seriously expect to defeat the coalition of the other two parties, but hoped to win 200 seats, which would have been a gain of 70 seats. However, intra-party conflicts between Banyat's southern faction and the Bangkok faction led by Abhisit Vejjajiva made this goal appear even less realistic. The Democrats also developed a populist agenda, promising more jobs, free education and health care, and combating crime and corruption. However, the party refused to give details of their policies.

The TRT's landslide victory cast doubt over the future of both party leaders, and Banyat resigned as Democrat Party leader immediately after the election. Abhisit Vejjajiva, Banyat's successor, said: "It will take a long time to revive the party because we need to look four years ahead and consider how to stay in the hearts of the people."

The Thai Rak Thai party was seeking to win an absolute majority in its own right, something no political party had ever achieved in Thailand at a genuinely free election. A coalition of other parties and civil society groups was formed to prevent this, arguing that Thaksin already had too much power and that giving him an absolute parliamentary majority would encourage what they alleged were his authoritarian tendencies. Prominent academic Kasem Sirisamphan, for example, accused Thaksin of running a "parliamentary dictatorship" and said that "people do not want a billionaire prime minister to further dominate the country and its politics."

Thaksin's party replied that it had provided Thailand with a stable, competent and corruption-free government, although critics said that corruption has actually increased under Thaksin's watch. Party spokesperson Suranand Vejjajiva said that Thais Love Thais was "the first party which could translate its populist policies into action. Its achievements and Mr Thaksin's vision give the party a clear edge and it will win an absolute majority," he said.

Thai politics tend to be regionally based. Thai Rak Thai is strongest in the north-east region (Isan), the poorest and most populated part of the country, where Thaksin's populist policies are most popular. TRT is also dominant in the north, since Thaksin was born in Chiang Mai and has directed much government spending to his home region. Thai Rak Thai is strong in the Chao Phraya valley as well, although the region has historically been a stronghold of Chart Thai, which still dominates in some of the central provinces. Voters in Bangkok, the wealthiest part of the country, are less predictable, but steady economic growth, goal-oriented campaign agendas like "Healthy Bangkok" and "10 new MRT lines across the capital"[1], and the publicity Thaksin received after the 2004 Indian Ocean earthquake was enough to swing the allegiance of the capital's middle-class to TRT. The Democrats are strongest in the south, but are popular among liberal-minded voters in Bangkok.