Thailand's liberal junior opposition Move Forward party garnered the most votes after Sunday's general election, with voters rejecting the incumbent pro-military government of Prime Minister Prayut Chan-o-cha, which has controlled the country for nearly a decade.

But the unexpected win by Move Forward and the second-largest number of seats captured Pheu Thai, an opposition party made up of supporters of former Prime Minister Thaksin Shinawatra, does not necessarily mean they will lead the next government due to an electoral system that favors the establishment.

Move Forward, which seeks for amending harsh laws against insulting the monarchy, has called for Pheu Thai, which is not keen about amending the law related to the monarch, and other parties to form a coalition.

Pita Limjaroenrat, the leader of Move Forward Party and a prime minister candidate, gives a press conference at the MFP headquarters on May 14, 2023, in Bangkok, Thailand. (Getty/Kyodo)

Of the 500 seats up for grabs in the House of Representatives, Move Forward, popular among young voters, won 152, followed by Pheu Thai's 141, according to unofficial results from the electoral commission.

The United Thai Nation Party, under which Prayut ran for re-election, gained only 36, ending fifth.

But Prayut still has a chance to be re-elected because elected members of the lower house and 250 military-appointed senators will determine the new prime minister through a vote expected in July.

Move Forward's leader, Pita Limjaroenrat, said at a press conference that he is ready to be prime minister, and has invited other political parties, including Pheu Thai, to join a coalition government to be formed "as soon as possible to avoid a political vacuum."

He expects his party, along with Pheu Thai and other opposition parties, to secure 309 seats, and by doing so, they would be able to form a coalition government.

Pita, 42, said he phoned Paetongtarn Shinawatra, Thaksin's daughter who is uniting Pheu Thai on behalf of her father in self-exile, to congratulate her and invited her party to join a government led by Move Forward.

Paetongtarn, 36, told reporters separately she was approached by Pita about partnering for a coalition government. But Pheu Thai has yet to decide whether or not to accept the proposal.

The opposition parties need at least 376 votes from the lower house members to take power because the senators are unlikely to support members of either Move Forward or Pheu Thai.

The 69-year-old Prayut, a former army general who had been in power for over eight years, faced a tough race as he met strong political opposition from Pheu Thai, which led opinion polls before the election, and Move Forward, reflecting an apparent appetite for change among an increasing number of voters.

After learning United Thai Nation trailed the opposition parties, Prayut briefly told reporters Sunday night that he would respect the result of the election being conducted democratically.

Pita also reiterated that the party will continue pushing for the amendment to the lese majeste law, under which insulting the king is punishable by up to 15 years in prison. Move Forward is the only party with a clear commitment to reforming the law.

The progressive party's election pledges included revoking military conscription and drafting a new constitution that would replace the current one enacted by the military in 2017.

Prayut staged a coup to topple the Pheu Thai-led elected government in May 2014 when he was the army chief and subsequently became interim prime minister of a military-run government.

In the 2019 election, Pheu Thai won the largest number of seats but failed to gather enough allies to form a government, prompting the second-place Palang Pracharath Party, which put forward Prayut as its candidate for prime minister, to take control with 18 other parties.

In 2020, student protestors swarmed the streets of Bangkok and other cities, calling for political reform and changes within the monarchy, traditionally viewed as an untouchable topic. Dozens of people have since been charged under the lese majeste law, with some running as Move Forward candidates in Sunday's election.

Supporters of Move Forward Party react to the election results at a bar near the party headquarters in Bangkok, Thailand, on May 14, 2023. (Getty/Kyodo)