Opposition leader is attempting to return to Cambodia from self-imposed exile to challenge Prime Minister Hun Sen.

Sam Rainsy, Cambodia’s most prominent opposition leader, has said he was not allowed to board a Thai Airways flight from Paris to Bangkok in his attempt to return home from self-imposed exile to challenge his country’s longtime leader.

Rainsy said on Thursday the Thai flag carrier “said they had received from very high up the instruction to not allow me to board”.

The leader of the Cambodia National Rescue Party (CNRP), who has been living in France since 2015, said he was “shocked” and “disappointed” by the move, and will “buy another ticket with another company” to return to Cambodia.

He accused Prime Minister Hun Sen of blocking his return.

“It’s shocking. I have done nothing wrong,” he told reporters in Paris. “This is all politics. I am a citizen, I have done nothing wrong so I must go back to Cambodia. Let me go to buy another ticket with another company.”

Rainsy and other opposition politicians were planning to return home on Saturday with followers to spark a popular movement to remove long-serving Hun Sen, who has clamped down on his opponents.

Hun Sen, who has ruled the country since 1985, has promised not to allow Rainsy to return, and sought support from regional neighbours to thwart the opposition’s plans.

Earlier on Thursday, the Malaysian government said it detained CRNP’s deputy, Mu Sochua, after she flew into Kuala Lumpur, while on her way to Cambodia.

Malaysian Prime Minister Mahathir Mohamad indicated Sochua would not be turned over to Cambodia but would instead be deported to an as-yet-undetermined third country.

Mahathir said Malaysia was bound by its principle of non-interference in neighbours’ affairs in the Association of Southeast Asian Nations (ASEAN).

“We do not want to let them use Malaysia as a base for struggle in other countries,” Mahathir told reporters. “We wanted to deport her … now we are trying to find any country that can take her.”

Earlier this week two other Cambodian opposition activists were arrested in Malaysia as they sought to fly to Thailand, but the country’s human rights commission says they will be processed by the United Nations refugee agency and then resettled in another country.