The International Commission of Jurists (ICJ) on Thursday urged the Department of Special Investigation (DSI) to expedite the probe into a high-profile disappearance case involving Karen rights activist Porlajee "Billy" Rakchongcharoen.
ICJ senior legal adviser Kingsley Abbott yesterday met DSI deputy director-general Korawat Panpraphakorn to follow up on the case after the agency accepted the issue as a special case on June 28.
"The ICJ has paid heed to this case because the victim is a Karen social activist which raises doubts over several issues, particularly whether state authorities were involved in Mr Porlajee's disappearance," he said.
"Therefore, the agency wants to expedite the pace of this investigation," Mr Abbott said.
He said the ICJ, an international human rights non-governmental organisation, was worried the case was moving at a glacial pace before the DSI accepted it. It now hoped for greater progress.
He hoped authorities would be able to track down the suspects to provide justice for the victim's family.
Mr Abbott stressed the investigation must be conducted in accordance with international legal standards and without any interference from other agencies.
Mr Abbott also mentioned a similar case, the 2004 disappearance of human rights lawyer, Somchai Neelapaijit, but said there was no evidence to indicate whether state authorities were embroiled in that case.
Mr Porlajee was last seen on April 17, 2014, in the custody of state officials.
At the time of his arrest, he was helping his relatives, a group of ethnic Karen, to sue Chaiwat Limlikit-aksorn, the former chief of Kaeng Krachan National Park, for setting fire to their bamboo huts and rice barns during a series of forest evictions.
Mr Chaiwat later claimed Mr Porlajee was arrested for collecting wild honey but was released after being given a warning.
Mr Porlajee's family was not convinced by Mr Chaiwat's account of events and decided to bring the case to court.
Mr Chaiwat and his team faced a murder charge related to Mr Porlajee's disappearance but were eventually acquitted due to a lack of evidence.
Pol Lt Col Korawat said the ICJ was satisfied that the DSI agreed to look into the case and it would cooperate with the DSI to compile evidence.
The agency has spoken to witnesses, he said, and the information will be used as a guideline in the investigation.