He was the only MP who did not report for work at the Secretariat of the House of Representatives on Monday.
Instead, he posted his resignation letter on Facebook on the day, saying it had been submitted to the House Secretariat.
In the resignation dated June 30, Pirapan said that though he had been elected in the May 14 election, he was still holding the post of secretary-general to outing Prime Minister General Prayut Chan-o-cha and would continue serving until the new Cabinet takes office.
In his Facebook post, Pirapan said he had sent his resignation to the House Secretariat on Friday.
“I choose to stand by Uncle Tu [Prayut] in the post of PM secretary-general until the last second of his office,” Pirapan’s post said.
As to why he has resigned as MP, Pirapan said it was because he loves and respects Prayut.
“It is my mission to complete this post and I have no hidden plans that some may think,” he said.