The body, in a full wetsuit and flippers, was found on Friday (Dec 16) tethered to a mooring post dozens of metres out to sea off Koh Larn – an island near the sleazy, crime-ridden beach town of Pattaya.
The macabre case has baffled detectives who say they are unable to ascertain how he died.
“The initial autopsy found his throat was slashed... but the forensic doctor said it could have happened by suicide or by someone cutting him,” Pattaya police colonel Apichai Krobpetch said.
“We believe he could be Russian... there are witnesses who said they heard him speaking Russian prior to his death,” he said, adding they were seeking consular help to identify the man.
Koh Larn is a short boat ride from Pattaya – a town located a few hours south of Bangkok and notorious for its go-go bars and links with organised crime.
The town is popular with Russian holidaymakers, who are met with Russian-speaking staff in some hotels and menus and street signs written in their language.
But its permissive atmosphere and sprawling red light district also hides a dark side.
Pattaya is infamous as a bolthole for criminals from across the world, including Russian underworld figures.