The missing boy, 11-year-old Supat Jampathong, a student at Wat Mongkolwararam School, was one of six friends playing in the shore break when they were overpowered by big waves and started being dragged away from the beach.
Two of the children were rescued by a local surfer, Norwegian national Terje Tonnessen, 37. The other three managed to scramble ashore by themselves.
The boys already brought to shore said they were playing in water only knee deep.
The search for Supat continues.
Thalang District Chief Adul Chuthong has informed Phuket Governor Norraphat Plodthong of the incident and that he has orderd the beach closed for swimming with red flags posted along the entire length of the beach.