Bangkok. The head of the progressive Thai political party that outpaced its rivals to a surprise first-place finish in May’s general election failed Thursday in his initial bid to have Parliament name him the country’s new prime minister.

The vote of a joint session of the 500-seat House of Representatives and 250-seat Senate saw Pita Limjaroenrat win 324 votes in the first round of balloting, short of the majority of 376 needed to become prime minister.

His Move Forward Party finished first in the May 14 election and afterward assembled an eight-party coalition that together had won 312 seats, a healthy majority in the lower house.

But strong opposition in the Senate, whose members are overwhelmingly conservative and generally opposed to the reformist platform of Pita’s party, seemingly doomed his chances in the first vote. Only 13 senators supported Pita's bid, while 34 voted against him and 159 abstained.

Pita told reporters afterward that he “accepted” the vote but was not giving up. He said the result was below expectations and thanked those senators who voted for him.

The biggest area of disagreement between the liberals backing Move Forward and the deeply conservative Senate is the campaign pledge of Pita’s party to amend a law that makes defaming the royal family punishable by three to 15 years in prison.

The monarchy is sacrosanct to members of Thailand’s royalist establishment, and even minor reforms that might improve and modernize the monarchy’s image are anathema to them. Move Forward’s coalition partners also have not endorsed the proposed legal change, and other parties ruled out joining the coalition because of the idea.

Much of the debate that preceded Thursday’s vote concerned the lese majeste law, also known as Article 112, which critics say is abused for political purposes.

The inconclusive finish to Thursday's voting sets the stage for another ballot, which is expected next week. Whether Pita will make a second effort, or step aside to let a nominee from another party in his coalition try their luck was not immediately known.