Muang Pattaya Police Station superintendent Pol Colonel Apichai Krobphetch called an urgent meeting yesterday morning to discuss the case.
Deputy Police Inspector Wattana Pradit said the case was expected to become a murder investigation.
"At the moment, we don't know his identity or even his nationality," Deputy Police Inspector Wattana Pradit said.
"All we can say is that the man is Caucasiasn and is around 173cm (5ft 6in) in height."
Officers went to the Ban Koh Larn area to gather more clues as a scuba diving team from the Sawang Boriboon Foundation and police returned to the scene to collect more evidence.
"We've put out a request to hotels, hostels and lodging houses to ask if any guests are missing," said police Superintendent Apichai Krobphetch.
"We've also asked foreign embassies to inform us if anyone reports somebody missing."