Thailand's parliament will hold a session on March 19 to vote on a new prime minister, House Speaker Sophon Zaram said on Monday, following last month's general election.

Caretaker Prime Minister Anutin Charnvirakul is seeking to be voted back to office by the new parliament after his Bhumjaithai Party won a clear victory in the February 8 election.

Thai King Maha Vajiralongkorn opened parliament on Saturday, as last month's general election result faces court scrutiny over barcodes on the ballots that may have violated the law.

The barcodes might undermine the secrecy of the ballot, said the country's Office of the Ombudsman, which petitioned the Constitutional Court to consider the case.

Prime Minister Anutin Charnvirakul's Bhumjaithai Party won a clear victory in the February 8 election, but the ombudsman said late on Friday that there had been 21 complaints from the public that barcodes and QR codes on the ballots could potentially be used to identify which party or candidate a given voter had chosen.

The court annulled a 2006 election on the grounds that the voting process had not been conducted in secret.

The Election Commission has said the barcodes were included for security purposes and that identifying a voter would require access to the upper half of the ballots, which were securely stored.