A missing schoolboy who was swept away into the sea druing a storm has been found dead in Thailand.

Students Mark and Wit, both 15, had ignored the red flag weather warning to play at Chaweng Beach in Surat Thani province during a school holiday on February 26.

However, they were struck by strong waves and carried away by currents into the sea.

Authorities on Wednesday were notified by resort staff who found a body believed to be Wit floating at the beach. The deceased was wearing blue shorts similar to Wit's attire on the day he went missing.

Two days earlier on February 26, his friend Mark's lifeless body was found drifting around 1.6 kilometres from where they disappeared.

The bodies of both boys underwent post-mortem examinations before being turned over to their families for funeral arrangements.

Meanwhile, Ratchaporn Poolsawadee, president of the Tourism Association of Koh Samui, reminded residents and tourists to heed safety regulations.

He said: 'Everyone must refrain from swimming at the beach when a red flag is raised due to the hazardous conditions caused by strong waves.

'Hotel operators should also play their part in warning tourists, who may not be familiar with the red flags, against swimming during these periods.'