The man's body was pulled from the surf off Nai Harn Beach this morning at about 8am.
The victim was named as Mr Ernst Krummenacher, 71, of Switzerland, who had lived in Phuket for six years.
Mr Krummenacher's son, Dion, told officers that he heard him yelling for help before dissapearing under the water. Friends proceded to attempt to rescue him, but by the time he was pulled ashore, it was too late.
Dion told officers that he believes his father suffered a heart attack while in the water.
The death of Mr Krummenacher follows the rescue of a 24-year-old Russian tourist yesterday at Surin Beach. On Thursday, a Korean man drowned off Patong and another Korean tourist drowned off Kata on Friday.
CORRECTION: The initial report from police said Dion was Mr Krummenacher's wife, not son. The error is regretted.