Forensic experts in Bangkok will try to unravel the mystery surrounding the death of an unidentified Westerner found in the water off Koh Phangan with a backpack filled with rocks.
The man's body is being sent from Surat Thani to the Institute of Forensic Medicine in Bangkok after he was found drifting off the popular resort island on Thursday.
Apichart Boonsriroj, the Surat Thani police commander, requested the forensic examination after police in Koh Phangan district were unable to reach a conclusion on the cause of death or identify the deceased.
The man, believed to be a European, was found in the Gulf of Thailand about 500 metres off the island on Thursday. He was wearing blue shorts and was shirtless. He was also wearing a backpack with five rocks among the items found inside.
Pol Col Kusol Pankerd, a deputy superintendent with the Koh Phangan police station, said on Thursday that the man may have been dead for up to five days.
Pol Maj Gen Apichart said there was no conclusive evidence of the cause of his death and did not rule out homicide.
The rocks inside the backpack could have been used to add weight for diving, but they could also have been used by a killer to weigh the body down, he added.
Police on Koh Phangan are asking all resorts to review their guest registers to determine if anyone is unaccounted for.