Malaysia has released three Cambodian political exiles it detained this week at the request of Phnom Penh, while the country's opposition leader has been prevented from boarding a flight to Bangkok from Paris — thwarting their attempt to go back home.

Key points: Mu Sochua was detained by Malaysian immigration officials on Wednesday night

Mu Sochua was detained by Malaysian immigration officials on Wednesday night Opposition leader Sam Rainsy was barred from boarding a flight from Paris to Bangkok

Opposition leader Sam Rainsy was barred from boarding a flight from Paris to Bangkok Human Rights Watch said Malaysia shouldn't do Phnom Penh's "dirty work"

Sam Rainsy, a former Cambodian finance minister and leader of the opposition Cambodia National Rescue Party (CNRP), was barred from boarding a Thai Airways flight destined for Bangkok from Paris despite holding a ticket in his name, which he posted on Twitter.

In Malaysia, CNRP vice-president Mu Sochua was detained on Wednesday night at a Kuala Lumpur airport, ahead of her planned return home to join Mr Rainsy and lead anti-Government demonstrations on Cambodian Independence Day this Saturday.

Mr Rainsy said Thai Airlines "said they had received from very high up the instruction to not allow me to board". ( AFP: Dominique Faget )

Jerald Joseph, an official of the Malaysian Human Rights Commission, said Ms Soucha — along with two previously detained CNRP youth activists — would stay in a hotel for now.

Speaking to reporters in Paris, Mr Rainsy said he was "very shocked and very disappointed".

He said the Thai flag carrier "said they had received from very high up the instruction to not allow me to board".

"I want to go back, my people are waiting for me," he said.

Mr Rainsy has vowed to find another flight.

When asked about Mr Rainsy's claims, a Thai Airways representative declined to comment, citing passenger confidentiality.

Who are Cambodia's exiles?

The former finance minister has been living in self-imposed exile in Paris since 2016. ( AP: Nicolas Garriga )

The CNRP was dissolved by court order in late 2017, allowing Cambodia's strongman ruler Hun Sen to sweep a 2018 general election with his Cambodian People's Party (CPP).

Cambodian courts are widely considered to be under the influence of the Government, which employs the law to harass its opponents.

These exiled politicians have previously openly stated their desire to unseat Cambodian Prime Minister Hun Sen, an autocratic leader who has clamped down on opposition.

Ms Sochua fled Cambodia in 2017 fearing arrest amid a mass crackdown on the opposition.

Human Rights Watch has called Mu Sochua's detention "absolutely ludicrous and unacceptable". ( AP: Achmad Ibrahim )

Mr Rainsy, a former finance minister, has lived in exile in France since fleeing Cambodia four years ago following a conviction for criminal defamation.

He also faces a five-year prison sentence in a separate case.

He says the charges were politically motivated to destroy opposition to Hun Sen.

The CNRP's leader inside Cambodia, Kem Sokha, was arrested on treason charges in 2017 and remains under house arrest.

Cambodian security forces have been put on high alert and scores of opposition supporters have been detained.

Why are Thailand and Malaysia on Phnom Penh's side?

Cambodia's opposition leaders want to return home in time for the country's independence day celebrations on Saturday. ( AFP: Tang Chin Sothy )

Hun Sen's Government has barred the opposition politicians' return, alerting airlines that they would be turned back, and also conveyed its position to neighbouring countries.

Hours before Ms Sochua's detention, the Cambodian Embassy in Indonesia called for her arrest after she gave a news conference in Jakarta.

Cambodian Ambassador Hor Nambora interrupted that news conference to describe the opposition politicians as "fugitives" and "criminals".

Loading

Malaysia's decision this week reflected that of Thailand's, which prevented Cambodian opposition officials from travelling through the country to Cambodia.

On Wednesday, Thai Prime Minister Prayuth Chan-ocha said Mr Rainsy would not be allowed to enter Thailand, citing an agreement between Association of Southeast Asian Nations (ASEAN) members not to interfere in each other's domestic affairs.

Loading

He was joined later by Malaysian Prime Minister Mahathir Mohamad who said he did not want Malaysia to be used as a base for political activists from the region, and had said he was trying to organise her passage to a third country.

"We are trying to find any country that can take her. We don't want to be at odds with other governments because this is not our affair, it's their affair," Dr Mahathir said.

"We are not in the position to deport people and neither do we like doing that,

"We are a pro-democracy government. We follow things very closely but at the same time, we cannot interfere with what happens in other countries."

The opposition's treatment by other Association of Southeast Asian Nations members was condemned by the ASEAN Parliamentarians for Human Rights (APHR) as a "complete disregard" for democracy.

"It is outrageous that Malaysia and other ASEAN countries are doing the dirty bidding of their counterparts fearful of legitimate political opposition," said APHR board member Kasit Piromya.

What happens from here?

Mr Rainsy met with his supporters after he was barred from boarding the Thai flight. ( Reuters: Charles Plantiau )

Cambodian officials have repeatedly warned that if the opposition leaders did make it back, they would immediately be arrested.

Most have convictions or charges pending against them, including inciting armed rebellion.

In the lead-up to Mr Rainsy's planned flight, Cambodian media outlet Voice of America (VOA) Cambodia reported that Cambodia's Ministry of Foreign Affairs had cancelled the passports of 12 people, including those of Ms Sochua and fellow opposition politician Eng Chhay Eang.

Earlier on Thursday, Mr Rainsy spoke to ABC's The World and said he was confident he would "overcome" the barriers preventing him from reaching Cambodia.

"They want freedom, they want justice for the Cambodian people. There will be many many Cambodians calling for change, then they will join our movement," he said.

He said the day's developments meant Hun Sen was "very afraid" of his group's return.

"Eventually democracy will prevail," he added.

Human Rights Watch (HRW) slammed Ms Sochua's detention as "absolutely ludicrous and unacceptable" and called for her release.

HRW Asia deputy director Phil Robertson said Malaysia should stand up to Cambodia's "bullying" of its regional neighbours and refuse to do Phnom Penh's dirty work in cracking down against the CNRP exiles.

ABC/wires