Lifeguard Ledet Sandod, 48, told police he was on duty when he saw the tourist* return from a swim shortly after midday. As the tourist reached knee-deep water, he suddenly collapsed face down.
Mr Ledet and a beachgoer rushed to help and called an ambulance. The tourist was taken to Chalong Hospital, but doctors confirmed he had died before arrival.
Pol Lt Col Surasak Sudmuang of Karon Police, who attended the scene, said no signs of assault were found on the body.
Police confirmed the tourist was a 68-year-old Swedish national who was staying at a nearby resort with friends.
The tourist had checked into the hotel on Aug 15 and was due to depart this Sunday (Aug 24). He was travelling with two friends, though staying in separate rooms.
Police have ordered a post-mortem examination to determine the cause of death.
* The Phuket News is withholding the man’s name until it has been confirmed his next of kin have been notified.