The body of a Korean man drowned when a long-tail ferry boat overturned on Sunday was found floating in the sea off Koh Phangan shortly before noon on Tuesday.

A boat captain reported finding the man's body at 11.33am.

He was found about 600 metres from Koh Phangan's Haad Rin pier, roughly five kilometres from where the long-tailed boat capsized early Sunday morning.

Police said the body was dressed in the same clothing the missing Korean man was seen wearing in security camera footage taken on Sunday. The body was sent to Koh Phangan Hospital for post-mortem examination. 

The Korean was among 10 tourists aboard the Pichitchai 38, a long-tailed boat taking them from Haad Rin beach to another beach on Koh Phangan. The boat capsized in high waves about 3am on Sunday. Nine of the passengers and the three boatmen were rescued.

Surat Thani's governor said the boat's owner would be charged with recklessness causing death. The boat was unregistered and driven by a man without a licence and who was a drug user and had ignored official warnings for all small boats to remain ashore due to the rough sea.

On Tuesday, red flags prohibiting swimming were placed along Haad Rin beach, where a New Year countdown was planned for later in the night.