Premchai will be summonsed to meet police and defend the allegation this week, a source said.
He and three others suspects were apprehended last week after forest rangers found him camping in a prohibited area, along with the remains of protected animals including a black leopard. Hunting rifles were confiscated from the campsite.
While Premchai has refused to talk to reporters, his lawyer claimed his innocence, saying his client was lost in the woods and had bought the fresh meat police found hidden near the campsite from a vendor.
Forensic officials revealed that the endangered big cat was hit by eight bullets.
Meanwhile, Premchai’s Land Cruiser, which was found at the campsite, was handed over to Thong Pha Phum police on Tuesday for forensic examination.
Premchai had a close aide inform officials that his trip was for the purpose of “nature study”.