Police are investigating after four foreigners were found dead off the coast of the holiday island Phuket in southern Thailand.

The first two men were discovered by local ship skipper Apiwat Kongsawat floating lifeless near Racha Noi island on Phuket's southeastern coast on December 29.

The seaman called the Thai Navy and tied the corpses to a buoy to prevent them from drifting away.

Officers arrived at the scene and took the bodies ashore at 5:15 pm local time. They were not able to identify them but believe they were not locals.

Bizarrely, the navy received yet another report of two more bodies found on the same island the following day on December 30.

Authorities discovered a foreign couple lying dead on the beach, with a Lagoon 42 catamaran boat found some 300 metres from the shore.

Officials are now trying to determine the foreigners' identities and the causes of their deaths.

Police Colonel Pichet Songtan from the Chalong district station said officers are now investigating.

He added: 'The initial notification was received from a local fisherman that two floating bodies were found, with the bodies bound with mooring buoys.

'Navy officers, paramedics and police attended the scene and helped to recover the bodies. They were tied together with thin rope about 20 metres long and wearing orange life jackets.

'We have started the legal process to investigate the cause of death and identify the deceased.'

The reports come after a German sailing enthusiast told police that his catamaran had gone missing from its mooring point in Nai Harn beach in Phuket on December 28.

Marco Cerefin, 58, said his vessel 'Marco Polo' - estimated to be around 300,000 USD - had disappeared, prompting a search mission that failed to turn up evidence.

The German national later said he believed no theft was involved, and that the yacht had simply dragged its anchor and drifted away.