Deputy Prime Minister Prawit Wongsuwon with Prime Minister Prayut Chan-o-cha in a water management event at the Royal Thai Army Club on Wednesday. (Photo by Wichan Charoenkiatpakul)

Deputy Prime Minister Gen Prawit Wongsuwon has signalled that he may not join the new cabinet and instead only act as an adviser to the prime minister, a source and close associate has revealed.

However, political observers believe Gen Prawit will remain highly influential and continue to work behind the scenes and wield his clout over the police and military to support the next government.

Earlier, sources said Gen Prawit would remain on as deputy prime minister in charge of security affairs in the next government, while Gen Prayut would concurrently serve as the defence minister, a cabinet post that Gen Prawit currently holds.

Defence Ministry spokesman Kongcheep Tantravanich said on Thursday that Gen Prawit would announce his decision regarding the part he will play in the next government by today.

However, Gen Prawit has repeatedly told the media over the past several days that he has not been in good health and is unsteady on his feet. "I cannot speak of his mind. But from his gestures and interviews over the past several days, he may be sending a retreat signal," Lt Gen Kongcheep said.

The source who is Gen Prawit's close associate said Gen Prawit, 73, wants to rest and focus on looking after his frail health.

Working five years in the government and the National Council for Peace and Order have exhausted him, the source said.

"He is still concerned for his younger brother [Gen Prayut]. But he will only work behind the scenes as an adviser," the source said.

Gen Prawit no longer wants to be the target of criticism, which he has been facing, especially over the luxury wristwatch scandal, the source said.

The source added Gen Prawit would find it hard to cope with fierce grilling from the opposition during censure debates if he joins the new government.

Observers noted that if Gen Prawit stays on in the next government, he may end up becoming its Achilles heel, vulnerable to attacks from opponents.

The source said Gen Prawit has not been in good health after undergoing heart bypass surgery in Switzerland two years ago.

After the surgery, he did not spend enough time recovering as he wanted to get back to work quickly, the source said, adding that Gen Prawit lost 10 kilogrammes immediately after the surgery.

Also post-surgery, he has to take regular care of health and travel to Switzerland every six months for regular health check-ups.

Meanwhile, a source at the Palang Pacharath Party (PPRP) said that after the new government is sworn into office, the party will hold a general assembly next month to nominate Gen Prayut as its new party leader replacing the incumbent leader Uttama Savanayana, as part of a restructure of the party's executive board.

The source said that after the new cabinet is formed, Mr Uttama will present a party membership application form to Gen Prayut to fill out before the party holds the meeting.

The source also said PPRP MP Nataphol Teepsuwan is tipped to be chosen as party secretary-general in replacing Sontirat Sontijirawong.

The source added the party wanted Gen Prayut to engage in politics over the long term and become a "fully-fledged" politician to stop criticism that he wanted to cling on to power.

But most importantly, the source said, Gen Prayut must take full control of the party to ensure various factions, especially the Sam Mitr (Three Allies) group, toe the party line especially when it comes to voting on important issues in parliament.

Sam Mitr previously was reportedly involved in the wrangling over the allocation of cabinet seats with coalition partners, especially with the Democrat and Bhumjaithai parties.

Deputy Prime Minister Wissanu Krea-ngam said on Thursday that if the new cabinet line-up is finalised by today, it will be sent to the cabinet secretary-general to check the qualifications of those on the cabinet list.

If the qualification checks are finished by next Tuesday, it can then be submitted for royal endorsement, Mr Wissanu said.