Patong Police were called to the scene, near Dolphin Square, at about 10am.
According to the initial report by police, Traiphop Buakhai, operating a parasail speedboat, was the first to spot the body floating face down in the water. He immediately notified lifeguards, who brought the deceased to shore.
The body of the tourist, whose identity has not yet been disclosed, was taken to hospital for medical examination, police reported.
Officers are conducting further investigations to determine the circumstances leading to the death, at this stage reported as a drowning.
In their brief report, Patong Police commended lifeguards and police patrol units for their prompt response.
Police urged tourists to remain cautious while engaging in water activities and to heed safety advisories.