Lawmakers in Thailand voted for a new prime minister, but the sole candidate failed to secure enough votes.

The leader of the progressive Move Forward Party, Pita Limjaroenrat, was the only nominee for the top job in Thursday's voting, after opposition parties scored a stunning victory in May's general election.

Pita needed support from more than half of the 750-seat bicameral parliament, but he fell short by 51 votes.

Earlier, some conservative lawmakers criticized Pita in the pre-voting debate over his party's campaign pledge to amend the royal defamation law.

One lawmaker said that amending the royal law would "only create conflict and division in Thai society and impact on Thai people's feelings."

Legal challenges are also looming. On the eve of the vote, the Constitutional Court accepted a complaint against Pita, alleging he held shares in a media company despite the constitution banning lawmakers from doing so.

Hundreds of Pita's supporters gathered near parliament ahead of the voting. They wore orange, the color of his party, and called on lawmakers to vote for Pita.

As Pita couldn't secure enough votes on Thursday, the House Speaker set dates for another round of voting in the next week.