The authorities have found fresh evidence relating to the mysterious disappearance of prominent Karen activist Pholachi "Billy" Rakchongcharoen.
Billy, who went missing on April 17, was last seen with the chief of Kaeng Krachan National Park in Phetchaburi.
It is known that the two men had had some conflicts.
Pol Lt-Colonel Korrawat Panprapakorn, who heads the Department of Special Investigation's Bureau of Regional Operation Centre, yesterday revealed that bloodstains were found inside a car belonging to the park.
"Although the car was already cleaned at the time of our examination, forensic techniques have allowed the detection of blood and further lab tests confirmed that the bloodstains come from a man," Korrawat said.
He added that further tests were being carried out to determine if the blood belonged to Billy.
Korrawat said officials at the Central Institute of Forensic Science Thailand had helped with the examination and tests.
"It's suspicious as to why human blood was found inside the car because the car's driver told us that the vehicle had never been used to carry any carcass or any dirty stuff," he said.