Flouting a Cambodian extradition request, Thailand on Friday deported alleged “terrorist” and fugitive Sam Serey to Denmark, prompting a Cambodian official on Sunday to express disappointment at the decision and threaten to ignore future Thai requests for extradition.

Serey – founder of the dissident group Khmer National Liberation Front, which the government has branded a terrorist organisation – confirmed the flight in a message on Friday evening, saying only, “I am now arriving in Denmark.”

Serey was arrested in Bangkok on Wednesday for overstaying his visa. On April 10, Prime Minister Hun Sen claimed he foiled a purported plot of Serey’s to bomb Wat Phnom and Siem Reap over the Khmer New Year holiday, offering little concrete evidence to support the allegation. Cambodian authorities put in a request for his extradition from Thailand on Thursday, citing Serey’s past convictions for trying to “topple the government”.

He was sentenced in absentia after being granted political asylum by Denmark.

In an interview on Sunday, Serey confirmed that he was in the process of renewing his already-expired visa when he was detained.

“My name is in the blacklist so they could not extend,” he said, adding that he was detained by immigration police before being transferred to the International Detention Centre.

On his way to the IDC, Serey was able to send messages to the UN, Human Rights Watch and the Danish Embassy.

“After that I did not get any information,” Serey said.Despite the seemingly dire situation, Serey said he was unconcerned throughout the ordeal. “I knew there would be intervention,” he said.

After around four hours in detention, Serey was released by Thai officials and ordered to buy a flight to Copenhagen immediately.

Despite his close call, and a five-year ban from Thailand, Serey pledged to return to the region to continue to “fight for democracy”.

“At this time, it was a big failure of Hun Sen’s, and a win for democracy,” he said.

Phil Robertson, the deputy director of Human Rights Watch’s Asia division, applauded the decision to return him to Denmark.

“Thailand deserves credit for making the right decision to respect Sam Serey’s continuing refugee status and sending him back to Denmark, the nation that is providing him with refugee protection,” Robertson said in a statement. “Clearly, the Royal Danish Embassy, UN agencies and other like-minded diplomats in Bangkok were very determined in persuading the Thai government to respect Sam Serey’s refugee status and not send him back to Cambodia.”

The Thai Ministry of Foreign Affairs did not respond to a request for comment.

Serey thanked Human Rights Watch, the Danish Embassy, the UN and Thai officials for helping him evade Cambodia’s extradition request.

The Danish Embassy, which was tight-lipped throughout the process, would only say on Sunday that the “case had the highest priority for the embassy”.

Serey is a permanent resident of Denmark, not a Danish citizen but has special travel documents issued by the country.

Robertson acknowledged that HRW played a critical role, saying the group “moved quickly to sound the alarm bell” when Serey was first detained.

“We talked to everyone here who we thought could play a role in influencing the decision – the Thai authorities, the UN, Bangkok-based diplomats and the media – to encourage an outcome that respected international human rights law by allowing him to return to Denmark,” he said in an email.

While Robertson was “elated” with Thailand’s decision, Cambodian government officials were angered.

Interior Ministry spokesman Khieu Sopheak said he regretted the decision to release the “terrorist”.

“We have an extradition agreement with them. Why did they do that to us? We are really disappointed,” he said. Sopheak said that next time maybe Cambodia would not heed Thailand’s requests for extradition.

“This time it is your turn, and next time it’s our turn,” he said.

“We are the neighbouring countries. We did not ask you for basil and lemongrass. We asked you for the prisoner,” he added.

Chum Sounry, spokesman for the Ministry of Foreign Affairs, said Cambodia has not yet received an official notice of the decision from Thailand.

Additional reporting by Phak Seangly and Daphne Chen