Thailand’s Criminal Court for Corruption and Misconduct Cases is to hold its first hearing in the murder case of ethnic Karen human rights activist Porlajee Rakchongcharoen, aka “Billy”, on Monday.

Three prosecution witnesses, including Porlajee’s mother Pirojee, his widow, Phinnapa Phrueksaphan, and a villager of Ban Bang Kloy in the Kaeng Krachan National Park in Phetchaburi province, are scheduled to testify.

The four defendants, including Chaiwat Limlikhitaksorn, former chief of the national park, and his three former subordinates, are to be present during the hearing. They were charged with premediated murder, abduction and illegal detention, among other offences.

Porlajee went missing after he was last seen on April 17th,2014, when he was arrested by a group of park officials, led by Chaiwat, for allegedly illegally collecting wild honey in the park. Chaiwat claimed that Porlajee was released after being questioned.

Phinnapa subsequently asked the Department of Special Investigation to open a special probe into the case, but the DSI rejected her request on the grounds that she was not legally married to Porlajee and thus had no standing to petition the DSI and that the DSI investigation could proceed if Porlajee’s body was not found.

Under pressure from rights groups, local and international, the DSI ultimately stepped in to investigate the case. They eventually found an oil drum, containing burned human remains, in a river in Kaeng Krachan national park.

DNA tests on skull fragments found in the drum, which were believed to be Porlajee’s, were found to be a partial match to his mother’s DNA.