Police said the victim, identified as Wimonrat Yang-aphai, was swimming about 50 metres from shore with a friend, Kasakorn Prayot, when both were caught in strong waves at around 4pm.
Security guards at a nearby resort and nearby residents rushed to help and called an ambulance.
Mr Kasakorn was rescued with minor injuries after choking on seawater, but Ms Wimonrat was pulled from the water unconscious and without a pulse.
She was rushed to Thalang Hospital, where doctors performed CPR but were unable to revive her. She was later pronounced dead.
Investigators confirmed there were no signs of violence on the body. The cause of death was recorded as drowning.
Ms Wimonrat’s family has requested her body be returned to her home province of Phatthalung for funeral rites.
Police noted that Ms Wimonrat was staying at a residence in Phuket Town.
She had come to Phuket to study, Thalang Police Chief Pol Col Nikorn Chuthong told The Phuket News.