General elections were held in Thailand on 24 March 2019. They were the first elections since the 2014 Thai coup d'état that installed coup leader General Prayut Chan-o-cha as prime minister, and the first held in accordance with the 2017 constitution, which was drafted under the ruling military junta. The elections selected the five hundred members of the new House of Representatives, the previous House having been dissolved by the coup.

Seventy-seven parties contested the elections, including the two major parties, Pheu Thai (which supported former prime minister Thaksin Shinawatra and held a majority of seats prior to the coup) and the Democrat Party (the main opposition party prior to the coup). They were joined by several new parties, which mostly campaigned on a pro- or anti-junta stance. The former included the Prayut-aligned Palang Pracharath Party, while the latter included the Future Forward Party, which catered to young voters, as well as several Pheu Thai–aligned parties.

The elections were held using a new mixed-member apportionment system, in which voters cast a single vote for both a constituency candidate and a nationwide party list, with the nationwide list used as leveling seats to achieve proportional representation. Under the new constitution, the prime minister did not need to be an elected member of the House, and would be chosen by the full Parliament, including the 250 members of the Senate, rather than only members of the House as previously.

The elections were widely seen as a skewed race in which Prayut had an unfair advantage, as the 250 sitting members of the appointed Senate were to be selected by the junta. The Royal Family was involved to an unusual degree; the Pheu Thai–aligned Thai Raksa Chart Party named Princess Ubol Ratana, the elder sister of King Vajiralongkorn, as its candidate for prime minister, leading to condemnation by the King and the party's dissolution by the Constitutional Court. In a move criticised on social media and interpreted as a political intervention, Vajiralongkorn issued a statement on the night prior to the election urging the public to support "good people" to prevent "chaos", quoting remarks by his father, the late king.

Overseas voting took place from 28 January to 19 February, and advanced voting took place throughout the country on 17 March. The main election took place from 08:00 to 17:00 on 24 March. Rights groups and election monitors criticized the election for its biased environment, and the Election Commission for many errors and irregularities. The announcement of the results was repeatedly delayed; unofficial results were announced on 28 March, four days after the election. Official results were announced on 8 May.

Although Palang Pracharath received the most votes and won 116 seats, Pheu Thai emerged as the largest party with 136 seats. Most of the remaining seats were won by the Future Forward, Democrat and Bhumjaithai parties. Pheu Thai and Future Forward announced a seven-party alliance soon after the election, but were unable to form a government. Parliament convened on 24 May and on 5 June voted to make Prayut prime minister.

Background Early general elections had been held on 2 February 2014 after Prime Minister Yingluck Shinawatra asked King Bhumibol Adulyadej to dissolve parliament more than a year early due to a political crisis. The leaders of the anti-government protests objected to the polls, instead demanding that there be "reform before elections" and the Yingluck government be replaced with a royally-appointed "reform council". The elections were thus boycotted by the main opposition party, the Democrat Party, and disruption by protesters meant that voting in some constituencies had to be delayed until a later date, while absentee voters in urban areas were unable to vote.

In April 2014 the Constitutional Court ruled that the election was unconstitutional because the vote had not taken place on the same day nationwide. Following an agreement between the Election Commission and Yingluck's government, the fresh elections were set for 20 July.Thailand to hold fresh election on 20 July BBC News, 30 April 2014 However, the elections were cancelled after a coup d'état in May deposed the elected government and installed a military government known as the National Council for Peace and Order (NCPO), led by General Prayut Chan-o-cha, then-Commander in Chief of the Royal Thai Army. The NCPO, on taking power, declared its intention to hold general elections after carrying out reforms and promulgating a new constitution.

Delays The date of the 2019 general elections had been subject to much speculation, given the uncertainty of Prayut and the junta since taking power in the May 2014 coup.

Shortly after the 2014 coup, Prayut said that elections would likely be held "by the end of 2015". By late 2014, however, several government officials had said publicly that elections would not be held until 2016, around mid-year.

In May 2015 Deputy Prime Minister Wissanu Krea-ngam said that elections would now be held "around August or in September" 2016, after the government announced its intention to hold a referendum on its draft constitution, which would likely be held sometime in early 2016.

In June 2015 Prayut said that he was willing to stay in office for another two years if people "wanted him to", following a push by the National Reform Council (NRC), a government body established by the National Council for Peace and Order (NCPO), to hold a vote on whether or not the government's reforms should be completed before elections were held. This would mean general elections might potentially not be held until early 2018, but a few days later distanced himself from the NRC's initiative after facing backlash for his remarks, saying "I'm not interested. It's all about the roadmap. Stop asking me [about the matter]."

In October 2017 Prime Minister Prayut pledged that a general election would be held sometime in November 2018. However, the selection of an election date gave way to rumours that Prime Minister Prayut would attempt to stay in power after the next election through a military-backed political party. While this was the case, in January 2018 Thailand's parliamentary body voted to postpone enforcement of a new election law by 90 days, further dragging out the timing of an election. At the time, the deputy prime minister said the parliament's decision could delay the election until February–March 2019.

On 3 January 2019 Deputy Prime Minister Wissanu Krea-ngam told that the election will be delayed citing the royal coronation ceremony as the cause of the delay. In response, former EC commissioner Somchai Srisutthiyakorn said the coronation doesn't affect the election and the previously promised 24 February date is still possible.

Although the election date has to be set by the Election Commission, they cannot do so until the government issues a royal decree formally announcing the election. The government did not issue a royal decree on 3 January as previously planned and has declined to say when they will do so.

On 10 January the Bangkok Post reported that 24 February date for the election was no longer possible because the government has not published a royal decree and the EC would need at least 45 days to prepare the election. The following day, Wissanu Krea-ngam announced that the royal decree will be released sometime in January, paving way for an election "no later than March."

Electoral system Changes to the voting system, introduced by the 2017 constitution, were first implemented in this election. Whereas previous general elections in Thailand since 2001 used a parallel voting system, with voters marking two ballots, one for their constituency and one for a nationwide party list, the new system, referred to as "mixed-member apportionment", uses a mixed single vote for both the constituency and the party list (which makes it a variant of the mixed-member proportional system). The 350 constituency seats are won by first-past-the-post voting as in previous elections. However, the 150 party-list seats serve a compensatory function, and are allocated so as to give each party a total number of seats proportional to the nationwide number of votes they received (top-up).

Other changes introduced by the new constitution are the removal of the requirement that the prime minister be selected from among the elected members of the House of Representatives. Instead, each party may name, in advance, up to three candidates to nominate as prime minister if they achieve a majority. Also, the prime minister will be voted on by the combined National Assembly, which also includes the 250 members of the Senate, Thailand's upper house, rather than only by the House of Representatives, as was previously done.

As the entire sitting Senate will be appointed by the NCPO, commentators say that the change opens up the strong possibility that Prayut will become Thailand's next prime minister despite pro-Prayut parties being predicted to win fewer seats in the House of Representatives. With the assumption that all 250 senators will support Prayut, pro-Prayut parties would only need to win 126 seats for him to be selected as prime minister.

Constituency boundary controversy Under the new constitution, the number of constituencies was reduced from 400 to 350. In 2018, the Election Commission (ECT) was tasked with drawing up new district boundaries. However, shortly before the ECT were about to announce the new boundaries, Prime Minister Prayut invoked Section 44 of the constitution to issue an order pushing back the deadline and delaying the announcement. The order also exempted the ECT from complying with existing districting laws and allowing them to draw constituency boundaries in any manner they wished.

The move sparked outrage from the Pheu Thai and Democrat parties and the watchdog organisation Open Forum for Democracy Foundation. They argued the purpose of the delay was to enable the ECT to draw constituency boundaries that favoured Prayut's Palang Pracharath Party. Some journalists and commentators compared this to gerrymandering, while others opined that the changes meant that the elections were a foregone conclusion.

Election Commission chairman Ittiporn Boonpracong denied the allegations, citing his eye surgery as the cause of the delay. The EC completed and released the new district constituencies on 29 November. Following the release, political parties and watchdog organisations stated that they had found several instances of gerrymandering that would benefit the Palang Pracharat Party.

Campaign In total, seventy-seven parties contested the elections. Among them are the two major parties of the previous elected house, Pheu Thai (the majority) and the Democrat Party (the opposition), as well as the smaller long-standing players Bhumjaithai, Chartthaipattana and Chart Pattana.

Several new parties also ran for the first time. The Palang Pracharath Party directly supported Prayut, and included several of his cabinet members. Other smaller pro-Prayut parties include the Action Coalition for Thailand, led by 2013–2014 protest leader Suthep Thaugsuban, and the People Reform Party, headed by Paiboon Nititawan.

On the opposing end, many parties took an anti-junta stance. These include several Pheu Thai–aligned parties, as well as other groups. As the election laws and regulatory bodies were seen as stacked and biased against their favour, Pheu Thai split off into a network of several smaller affiliated parties in order to distribute their risk from legal intervention. These parties were Thai Raksa Chart, Puea Chat (consisting of several United Front for Democracy Against Dictatorship leaders), and Prachachart.