KUALA LUMPUR (REUTERS) - Hours after Malaysia's change of leadership at the weekend, former prime minister Najib Razak posted a picture of himself smiling and giving a thumbs up on social media.

It was tagged as a gesture of satisfaction with a restaurant meal, but many Malaysians saw it as a bigger sign of happiness from a man who was driven from office in 2018 and is now on trial for corruption over the multibillion-dollar 1MDB fund scandal.

With the return of Najib's party to power after a week of political turmoil, and therefore being in a position to influence policy, some Malaysians were questioning whether it will affect the handling of the high profile trials.

Tun Dr Mahathir Mohamad, who was ousted as prime minister in last week's realignments, accused Najib and his party of engineering last week's political crisis to help them avoid conviction.

"If Najib can be part of the government now, he can do all sorts of things to free himself," the 94-year-old told a meeting with his party's youth members on Sunday.

Ms Cynthia Gabriel, director of the Kuala Lumpur-based anti-corruption watchdog C4 Centre, said: "The worst-case scenario is that these grand corruption trials will be dropped through judicial interference and more."

Najib has said he hopes to continue to fight his case in court.

In his first message, new Prime Minister Muhyiddin Yassin said fighting corruption would be a priority for his government, whose biggest backer in Parliament is Najib's United Malays National Organisation (Umno).

The prime minister made no specific mention of the trials.

Mr Muhyiddin took over on Sunday from Dr Mahathir, who had ousted Umno in 2018 amid anger over the 1MDB scandal that stretched from Malaysia to the Middle East to Hollywood. Najib, his wife, Umno's leader and others were quickly put on trial for corruption.

The US Department of Justice estimates US$4.5 billion (S$6.3 billion) was misappropriated from Malaysia's 1MDB sovereign fund between 2009 and 2014.

US and Malaysian authorities say over US$1 billion stolen from 1MDB flowed into Najib's personal banks accounts.

The case has also led to scrutiny of Goldman Sachs, which Malaysia has accused of misleading investors over bond sales totalling US$6.5 billion that the bank helped raise for 1MDB.

Three units of the bank have pleaded not guilty.

Najib is facing five trials, the first of which - involving seven charges linked to US$10 million misappropriated from a 1MDB unit - is expected to reach a verdict within months.

He has consistently denied wrongdoing, saying he was misled by Malaysian financier Jho Low and other 1MDB officials.

MULTIPLE TRIALS

Among 10 others on trial for corruption are Najib's wife, Rosmah Mansor, and Umno party leader Ahmad Zahid Hamidi.

Mr Muhyiddin's office did not respond to a request for comment on what would happen to the trials now.

Najib did not respond to requests for comment but told reporters on Monday that he hoped to continue fighting his case in court.

"We'll go through the court process," he said. "It's the only credible way."

A senior Umno official echoed Najib's sentiments, saying the new government should not interfere in the courts.

"If we interfere by withdrawing cases of those charged, the people would say the government does not respect the law and the judicial body is not independent; so, don't mar that concept," party secretary-general Annuar Musa told state news agency Bernama.

Although Najib was quick to post congratulations to Mr Muhyiddin on social media, their relationship has been strained.

Mr Muhyiddin was fired by Najib as his deputy in 2015 after questioning his handling of 1MDB.

That led Mr Muhyiddin to form the new party with Dr Mahathir that brought them both back into office before it was torn apart in the recent political fighting.

Najib had not been directly involved in coalition talks even if he had tried to encourage Dr Mahathir's downfall from behind the scenes, said one source close to the new prime minister who did not want to be identified.

"Muhyiddin doesn't want to deal with Najib," the source said.

Mr Muhyiddin pointedly emphasised "efforts to stamp out corruption" in his first public speech on Monday.

Despite his fall, Najib is an elected lawmaker and remains a senior figure within the Umno party. He has a large popular base.

His Facebook page has 3.9 million likes compared with 3.6 million for Dr Mahathir's and fewer than one million for Mr Muhyiddin's.

Workers at the Indian Muslim restaurant where Najib posted his selfie after Mr Muhyiddin's swearing-in said he had been in a particularly good mood on Sunday.

"No matter how busy with politics, don't forget to eat first. Love yourself first," Najib's Facebook post said.