PHNOM PENH, Cambodia — Cambodia freed a Thai man pardoned for spying on Thailand's fugitive ex-prime minister on Monday, but his release was unlikely to end the controversy in a case that has strained relations between the neighbours.

The arrest of Siwarak Chothipong has been a major issue both in bilateral relations and Thai domestic politics because of the involvement of former Thai Prime Minister Thaksin Shinawatra, ousted in a 2006 military coup.

Thaksin is a fugitive from Thai justice, but was appointed an adviser to the Cambodian government and given a VIP welcome last month by Cambodian Premier Hun Sen.

Siwarak, who worked for a Thai-owned air traffic control company in Cambodia, was convicted of passing Thaksin's flight plans to the Thai Embassy. He was convicted last week of stealing information that could impact national security and sentenced to seven years in prison. Cambodian King Norodom Sihamoni pardoned Siwarak on Friday.

Hun Sen presided over a ceremony at his residence to mark Siwarak's release into the custody of his mother and Thai opposition politicians.

"From now on Siwarak has his freedom and can carry out any business," Hun Sen told reporters.

Thaksin arrived Sunday in Cambodia on a new visit and met Siwarak before his release. Cambodian government spokesman Khieu Kanharith said his pleas for leniency played a role in Siwarak's release.

Siwarak's conviction followed Cambodia's decision last month to name Thaksin as its special economic adviser. The appointment and Thaksin's subsequent visit to Cambodia angered the government in Bangkok and resulted in a recall of ambassadors from both sides.

There is widespread suspicion in Thailand that Siwarak's case was orchestrated to allow Thaksin to step in behind-the-scenes to secure his pardon -- a move that would promote Thaksin's image back home and embarrass the Thai government, which has tense relations with Cambodian Prime Minister Hun Sen.

Thaksin served as prime minister of Thailand from 2001 to 2006, when he was ousted in a military coup after being accused of corruption and showing disrespect to the monarchy.

He fled into self-imposed exile last year before a Thai court found him guilty of violating a conflict of interest law and sentenced him to two years in prison.

Thaksin's supporters and opponents have repeatedly taken to the streets since 2006 to spar over who has the right to rule the country, sometimes sparking violence.

Siwarak's mother and Chavalit Yongchaiyudh, leader of the Thaksin-linked Pheua Thai opposition party in Thailand, submitted a written request for the pardon to Hun Sen, who forwarded it to the king, Khieu Kanharith said. Thaksin spoke to Hun Sen by telephone to request the pardon.

Eang Sophalleth, a spokesman for Hun Sen, on Monday described Siwarak as a victim in the affair, and blamed the diplomat at the Thai Embassy who requested Thaksin's schedule from him. Cambodia expelled embassy First Secretary Kamrob Palawatwichai for activities incompatible with his position, which is usually a diplomatic euphemism for spying.

"He did not know that the magnitude of this crime," he said of Siwarak. "Without any request, Siwarak would not have been victimized like this."

Siwarak told reporters as he left Hun Sen's home Monday that he appreciated Hun Sen's and King Sihamoni's helping grant him his freedom.

"Today I will leave here, and first go back to Thailand," he said. "I think I will come back here."