Prime Minister Prayut Chan-o-cha on Thursday announced that Labour Minister Sirichai Distakul has resigned, as Deputy Prime Minister Prawit Wongsuwon denied there is a rift in the cabinet - but he will not be nominating Gen Sirichai's successor.
The deputy prime minister normally supervises the labour portfolios.
Gen Prayut 's announcement in the Royal Gazette said Gen Sirichai had tendered his resignation on Wednesday, and it was effective immediately.
The prime minister later told reporters that Gen Sirichai resigned to attend to private business. Work at the ministry would not be disrupted, Gen Prayut said, because he was supervising it.
The minister's resignation was widely anticipated on Wednesday, when Gen Prayut suddenly transferred Varanon Peetiwan, director-general of the Employment Department, to the post of deputy permanent secretary for labour.
The transfer was ordered in Gen Prayut's capacity as chief of the National Council for Peace and Order. It preceded the abrupt resignation of Gen Charoen Nopsuwan, vice minister of labour, on the same day. Aides of Gen Charoen and Gen Sirichai have moved their bosses' belongings out of the Labour Ministry.
On Wednesday Gen Sirichai had a 10 minute meeting with Gen Prayut at Government House, but Gen Prayut said he was not given a resignation letter.
On Thursday, Gen Prawit, who is deputy prime minister and defence minister, said the labour minister's resignation did not mean there was a rift within the cabinet. It was a personal decision, and Gen Sirichai had not informed him of it in advance, Gen Prawit said.
He also denied it had anything to do with any issue involving migrant workers or human trafficking. It could relate to Gen Sirichai's former work.
Although he supervises the labour ministry as deputy prime minister, Gen Prawit said he would not propose a successor of Gen Sirichai. He said Gen Prayut would decide that.
Gen Prawit said fewer military officers would remain in the cabinet. He ruled out the possibility of any portfolio changes at Defence.
Deputy Defence Minister Udomdej Sitabutr said on Thursday, in response to questions, that no one had proposed that he become the new labour minister.