The Department of Special Investigation (DSI) will begin searching for new clues in the disappearance of Karen rights activist Porlajee "Billy" Rakchongcharoen by reexamining a bloodstain found in a car owned by Kaeng Krachan National Park.
The DSI will ask for a fresh forensic analysis to be carried out on blood found on the rear seat of a car owned by the national park, which was at odds with Mr Porlajee over its orders to evict a Karen ethnic group from the protected forest in Phetchaburi.
Previously, authorities were only told the blood belonged to an unidentified male, DSI chief Paisith Wongmuang said yesterday.
However, the DSI now plans to ask the Central Institute of Forensic Science for a new examination, as well as consider the possibility of having it checked by a laboratory abroad.
Others evidence, including footage from security cameras inside the national park will also be looked at again, Pol Col Paisith added.
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 event 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.
According to a source, the DSI agreed to look into the case following complaints by international organisations over enforced disappearance cases in Thailand.
The International Commission of Jurists, Amnesty International and Human Rights Watch have been monitoring the case involving Mr Porlajee closely.
Yesterday, they issued a joint statement welcoming the fresh move and calling on authorities to bring those involved in the disappearance, "irrespective of rank or status", to justice.
The organisations also called on Thailand to expedite long overdue legal and administrative measures against enforced disappearance, in compliance with international human rights obligations.