Mr Tosawat, 24, a medical student at Rangsit University was doing a "practice dive" at about 13 metres depth, under the watch of an unnamed dive instructor early this afternoon in the area of Ko Miang's island number 7, located in the south of the Similan Islands National Park, some 85 kilometres northwest of Phuket.
While diving Mr Tosawat gave signal to his instructor that his head was spinning and was subsequently brought to surface, where Mr Tosawat was said to have lost consciousness.
The Area 3 Naval base was alerted at about 1:40pm, and an emergency rescue operation was ordered promptly.
The navy dispatched a helicopter to conduct an air-evacuation from Koh Hoo Yong island, where the patient was stabilised by paramedics and flown to Phuket Provincial Police headquarters in Phuket Town, where he was then transported by ambulence to hospital a few blocks away.