An unidentified tourist has washed up dead on a beach in Thailand with a one-kilogram rock strapped to his back.

The man, whose nationality is not known, turned up lifeless around 200 metres from the Nam Sai Beach on Samae San Island off the coast of 'Sin City' Pattaya on November 17.

He had fair skin and a goatee, but no wounds on his body. Police believe he was in his 40s.

The apparent murder victim was also shirtless, wearing tri-coloured swimming shorts and a backpack containing cigarettes, condoms, and a rock weighing one kilo.

Police did not find any identification documents in his bag.

Speaking to local media, a navy officer who found the corpse said: 'I was conducting regular beach patrols when I noticed the body floating in the middle of the sea.'

The corpse had already begun decaying when it was found as it is believed the man has been dead for more than two days.

Kawin Juirod, Deputy Inspector of the Sattahip police station, said: 'The tourist may have fallen into the sea or committed suicide. He had no wounds on his body.'

However, investigators were not ruling out the possibility of murder - with throwing foreign men off boats with a rock strapped to their back a known method of settling scores in the notoriously corrupt city.

The body has been taken to the Institute of Forensic Medicine for an autopsy.

Officers said they will be looking through missing persons records to find the man's identity.

Inspector Juirod added: 'The identity of the man has still not been established. We have no suspects until we know who he is.

'There is no clues about where he entered the water.'

Pattaya is a city on the east coast of Thailand best known for its round-the-clock nightlife, endemic corruption and bustling sex industry that has led to it being called a modern-day Sodom and Gomorrah or Sin City.

It attracts millions of tourists each year as well as fugitives from across the world who can take advantage of the lack of law enforcement and network of gangs.