A meeting at the parliament on Thursday is expected to set a date for the next joint session to vote for a new prime minister.
The meeting will follow Wednesday's rejection by the Constitutional Court of petitions by voters seeking to defend the right of Move Forward Party leader Pita Limjaroenrat to be renominated for prime minister on July 19, after he failed to get the needed support on July 14.
House Speaker Wan Muhamad Noor Matha, the ex-officio parliament president, said before the scheduled decision on Wednesday that the parliament would call a meeting of legal experts on Thursday to discuss a date for the next parliamentary vote for a new prime minister. The meeting would also consider the agenda for the debate.
Observers now expect the joint sitting to be either this Friday or next Tuesday, Aug 22.
Complainants in the case were all voters and included Assoc Prof Pornchai Theppanya and Assist Prof Boonsong Chalaythorn, who both voted for MFP in the May 14 general election. Another complainant was MFP MP Panyarat Pusitanont.
They filed their petitions with the court through the Ombudsman, complaining the parliament's rejection of Mr Pita's renomination affected their constitutional rights.
The Ombudsman forwarded these complaints to the charter court last month.
The joint sitting on July 19 rejected Mr Pita's renomination on procedural grounds, citing regulation 41 that forbids the reintroduction of a failed motion during the same session, including the nomination of a prime minister. Mr Pita's supporters argued that it applies to general business, not to the nomination of a prime minister.
On July 24, 115 law lecturers from 19 institutions also expressed their opposition to the parliament's passing of the resolution on July 19 to block the renomination of Mr Pita.
Mr Wan delayed the prime ministerial vote on Aug 4 after the Constitutional Court postponed its ruling.
On an urgent motion raised by MFP MP Rangsiman Rome for parliament to review its July 19 resolution rejecting the renomination of Mr Pita, Mr Wan said he would ask parliamentary officials to prepare session procedures and invite the Senate and the House whips for a meeting before the next parliamentary session.