No police officers are likely to take part in the anti-government protest on Tuesday and rally against alleged unfair police promotions, according to the Royal Thai Police (RTP).

The United Front of Thammasat and Demonstration, an ally of the anti-government Ratsadorn movement, will stage a protest at Ratchaprasong intersection at 5pm on Tuesday.

Expected to dominate the protest agenda on Tuesday is the "police tickets" allegation raised in last week's censure debate, zeroing in on Prime Minister Prayut Chan-o-cha and his deputy, Prawit Wongsuwon, who are both accused of turning a blind eye to the unusually swift promotions of unqualified police officers.

Gen Prawit oversaw the Police Commission which finalises senior police reshuffle lists while the coup-engineering National Council for Peace and Order was in power. He was later succeeded in the role by Gen Prayut.

The protest group urged police officers who want to make a stand against malpractice to join in the rally and make their voices heard.

RTP spokesman Yingyos Thepjamnong said officers know better than to participate in a protest and render themselves lawbreakers in the process.

The only officers present will be those on duty to observe the situation.

Last Friday, the opposition claimed during the no-confidence session in parliament that the "police tickets" privilege had led to much jockeying for senior posts in the force.

The alleged malpractice had to do with certain criteria set by the Police Commission having been waived so promotions could be offered to undeserving officers.

The opposition also alleged a high-ranking police commissioner last year sought the national police chief's support for the appointments of three senior officers who are not under his direct supervision. The commissioner himself also benefited from the privilege, having risen rapidly up the echelons.

On Monday, Gen Prayut said all candidates for promotion were carefully screened by a number of committees and insisted it was inconceivable to think that promotions were granted for reasons other than merit alone.

Meanwhile, the Criminal Court on Monday rejected bail requests made on behalf of the four leaders of the Ratsadorn anti-government protest movement.

It marked yet another failed attempt to secure release on bail four protest leaders charged with breaking Section 112 of the Criminal Code, the lese majeste law, sedition, violating the Ancient Sites Act and lesser charges for their roles during a rally at Sanam Luang on Sept 19.

The four are Arnon Nampa, Parit "Penguin" Chiwarak, Somyot Prueksakasemsuk and Patiwat "Mor Lam Bank" Saraiyaem.

The court denied the request, the third time so far, citing the same reasons for the dismissals of the previous two requests -- the offence carried a heavy penalty and there were reasons to believe the suspects would repeat the offence if released.