Cambodia's self-exiled opposition figurehead Sam Rainsy said Tuesday he had not given up on getting home after an initial bid to return was thwarted, and external pressure on strongman Hun Sen would force him to change course.

Rainsy spoke to AFP in Malaysia after flying in at the weekend from France, where he has lived since 2015, as he sought to fulfil a vow to return home by Independence Day on Saturday.

Hun Sen, who has ruled Cambodia since 1985, had denounced efforts by arch-rival Rainsy and other exiled opposition members to come home as a coup bid and ultimately stopped them with threats of arrest and by pressuring neighbouring countries.

Thailand, from where Rainsy had planned to cross into Cambodia, barred him from transitting and he was then prevented from getting on a flight to the kingdom, forcing him to head to Malaysia.

The former finance minister said however he was still "ready to go back to Cambodia at any time" and planned to head to Indonesia for several days from Wednesday, rather than returning to Europe.

"Things can change, I think things are going to change very quickly... it depends on Hun Sen," said the 70-year-old, who fled overseas to escape convictions he claims are politically motivated.

He did not give further details and it was not clear what was fuelling his optimism. But he has in the past cut deals with the strongman to get back to Cambodia, and analysts say without an agreement returning is impossible.

The authoritarian leader is facing international pressure following an opposition crackdown -- dozens of activists have been arrested in recent weeks -- and last year's one-sided elections which were swept by the government.

A major source of pressure is the European Union, which is considering revoking a duty-free tariff scheme for the poor nation's garment sector.

Rainsy said Hun Sen would have to shift course as criticism mounted: "The European Union is putting stronger and stronger pressure."

"There is a combination of internal pressure and external pressure -- the two combined will have a decisive influence," he added.

Sam Rainsy said he was 'ready to go back to Cambodia at any time'
Sam Rainsy said he was 'ready to go back to Cambodia at any time' AFP / Mohd RASFAN

There is little sign of vigorous, public opposition to Hun Sen's rule within Cambodia, however.

The only serious opposition group, Rainsy's Cambodia National Rescue Party (CNRP), was dissolved before last year's polls while Cambodians did not heed his call to come out onto the streets at the weekend.

The CNRP does still enjoy broad public backing and made major gains at 2013 polls, but Rainsy's long absence has made it hard for him to maintain his support base and achieve his aim of restoring democracy to the nation of 16 million.

However there have been signs Hun Sen -- who has tightened and loosened his chokehold on his opponents at will during his long reign -- is giving some ground after recent criticism.

Kem Sokha, a co-founder of the CNRP, was freed from house arrest at the weekend more than two years being charged with treason and accused of plotting to overthrow the government.

But Rainsy said the move was a small step, adding: "I think nobody is fooled by Hun Sen's attempts at having made concessions."

He met lawmakers at the Malaysian parliament Tuesday as he seeks to rally support across Southeast Asia in his push for greater democracy in Cambodia.

Last week before Rainsy's arrival in Malaysia, immigration officials detained the deputy of his party, Mu Sochua, after she flew in from Indonesia, acting on a request from Cambodia.

But she was released within a day following an outcry from rights groups, while Rainsy was allowed to enter the country unimpeded.

"Hun Sen has accused me and continues to accuse me of being a criminal," he said. "The fact that I can come to Malaysia, and be considered as a free man, this is a moral victory."