UPDATE 4-Cambodian opposition founder says he was blocked from boarding plane home from Paris

Cambodia's self-exiled opposition party founder Sam Rainsy, who has vowed to return to his home country to lead demonstrations against authoritarian rule, said he had been prevented on Thursday from checking-in for a flight from Paris to Bangkok. Rainsy apparently being barred from boarding came a day after Malaysian detained his party's vice president, Mu Sochua, at an airport and said it would deport her to a third country.

Cambodia's longtime Prime Minister Hun Sen, whose government has arrested some 50 opposition activists inside Cambodia and deployed troops to the border, has characterized the returning leaders' planned rallies as an attempted coup. Rainsy told Reuters at Paris' Charles de Gaulle Airport that Thai Airways staff refused to allow him to board but that he would not be deterred from trying again.

"I'm not allowed to board. They said they have received from very high up the instruction not to allow me to board," he said. "I'm very shocked, I'm very disappointed. I want to go back, my people are waiting for me."

A Thai Airways representative declined to comment, citing passenger confidentiality, responding to a question in an instant messaging forum with reporters. Rainsy, former finance minister and the founder of the now-banned opposition Cambodian National Rescue Party, 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. DEPORTATION THREAT

Rainsy said he would risk his own arrest to return by Saturday - Cambodia's independence day - and lead demonstrations against Hun Sen's one-party rule. Thailand had also refused entry to Mu Sochua, former women's affairs minister, on Oct. 20. Using her U.S. passport, she then flew to Indonesia and then Malaysia, where she was detained at Kuala Lumpur International Airport.

Malaysia this week also detained two other opposition leaders trying to fly to Thailand, presumably to cross into Cambodia by land. Malaysian Prime Minister Mahathir Mohamad indicated on Thursday that Sochua would not be turned over to Cambodia but would instead be deported to an as-yet-undetermined country.

"We do not want to let them to 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." The United States was aware of Sochua's situation, a U.S. government spokesman said. He would not comment further due to privacy restrictions.

Mu Sochua fled Cambodia in 2017 fearing arrest amid a mass crackdown on the opposition. The CNRP's leader inside Cambodia, Kem Sokha, was arrested on treason charges in 2017 and remains under house arrest.

Cambodia's Supreme Court later dissolved the CNRP. The party of Hun Sen, who has ruled Cambodia for more than three decades, went on to win all the seats in parliament in an election last year. 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.

Also Read: UPDATE 3-Facing arrest, Cambodia's Sam Rainsy will get home come what may