The government said Saturday it was not easy trying to secure the early release of Thai Patriots Network leader Veera Somkwamkid from a Cambodian jail through a prisoner exchange scheme.
"The government will explore all possible approaches and choose the appropriate one to secure his freedom," Foreign Minister Surapong Tovichakchaikul said.
He said Veera would have to complete two-thirds of his prison term to be eligible to apply for a royal pardon under Cambodian law.
As for a prisoner exchange programme, which is what Veera wants, Mr Surapong conceded it would be difficult as all of the Cambodian prisoners detained in Thailand were guilty of drug trafficking, illegal entry and general criminal cases, while Veera was sentenced on a national security violation and espionage.
"We are not closing the door on this possibility but we have to review the rules, terms and conditions," he said.
Veera said during a ceremony to mark the release of Thai Patriots Network activist Ratree Pipattanapaiboon on Friday that he would lodge an appeal to be considered for an exchange programme to spend the remainder of his jail term in Thailand from the end of this month when he would have served one-third of his sentence.
Veera and Ms Ratree were sentenced to eight and six years in jail respectively at Cambodia's Prey Sar prison for illegal entry, espionage and entering a restricted military zone without permission.
Veera still has to serve five years and six months in jail after Cambodia's Ministry of Justice reduced his sentence by six months.
Mr Surapong said the government was doing all it could to take care of Veera.
He thanked the Cambodian government for releasing Ms Ratree.
The release of Ms Ratree and a reduced jail term for Mr Veera were the culmination of talks between Prime Minister Yingluck Shinawatra and her Cambodian counterpart Hun Sen, said Mr Surapong.
"Things proceeded as the Cambodian prime minister promised," he said.
Democrat spokesman Chavanond Intarakomalyasut called on the government to speed up its efforts to help Veera.
He urged the government to ask Phnom Penh to further reduce his jail term so that the time spent in prison would meet the conditions for seeking an early royal pardon.
Pheu Thai deputy spokesman Jirayu Huangsap said the government could ask for a jail term reduction or seek a transfer so Veera could serve the remainder of his sentence in Thailand.
A reduced jail sentence would allow Veera to apply for a royal pardon sooner, he said.
Meanwhile, Ms Ratree who returned to Bangkok on Friday night vowed to fight for Veera's early release.
She told Bangkok Post Sunday that she would put all of her effort into helping him but had yet to talk to his mother, Wilaiwan Somkwamkid, about the next step.
Ms Ratree said she was very concerned about Veera's health and had begged him to take care of himself as best he can while behind bars in Cambodia. She said many Thais were giving him moral support.
The pair embraced before Veera was put into a prison van on Friday to be returned to his detention centre after the ceremonial ritual release of Ms Ratree.
She said it was difficult for her to be happy about her release when Veera was still in prison.
Ms Ratree thanked the Thai people, especially Thai Patriots Network members, for their moral support over the past two years. She said she had done the right thing for the country.
Veera and Ms Ratree as well as five other Thais were arrested by Cambodian authorities on Dec 29, 2010 while inspecting a disputed border area near Sa Kaeo's Ban Nongchan.
"I don't know yet how to restart my life. I have no idea what I'll do. I have not made any plans yet. First of all, I want to spend my life with my mum, my dad, and my family members to make up for lost time," she said.
Asked whether she would return to work with the Thai Patriots Network and its move on land demarcation between Thailand and Cambodia, Ms Ratree would not answer the question. However, she said she might resume her private business.
Surapol Maneepong, minister counsellor attached to the Thai Embassy in Cambodia, who led embassy officials to the ceremonial ritual to release Ms Ratree and other prisoners on Friday, said the embassy would do its best to take care of Veera.
"We assure you that we will help care for him the best we can until he is set free from Prey Sar prison," Mr Surapol said.