A 12-year-old boy Russian boy who was aboard a ferry that sank in Thailand on Sunday has died in hospital, an official in the Russian Embassy in Bangkok said.

His mother remains hospitalized in Thailand with facial injuries and a "very grave psychological condition," while the boy's father has arrived in Thailand from Russia, the official said, Interfax reported Thursday.

Four Russian citizens were hospitalized after a ferry carrying mainly foreign tourists went under water in the Gulf of Thailand not far from Pattaya, killing six people and seriously injuring 20 other. About 200 people were saved.