Page "Prime Minister of Thailand" Paragraph 7

To be appointed the nominee for the office must have the support of one-fifth of the members of the House of Representatives.

Then after a simple-majority vote in the House, a resolution will be passed and submitted to the King of Thailand, who will then make a formal appointment by giving his royal assent to the resolution.

This must be done within thirty days of the beginning of the first session of the House of Representatives after an election.

If no candidate can be found within this time then it is the duty of the President of the National Assembly of Thailand to submit the name considered most worthy for the King to formalize.