Maids at the resort noticed the man had not left his room yesterday and checked around 8.30pm.
They found the man naked, face-down on the bathroom floor, near the toilet.
He probably died from the blow when his head hit the floor, according to paramedics and investigating officers from Kathu Police Station.
Police believe there were no suspicious circumstances. Paramedics estimated he had been dead for about five hours.
The man, aged 41, was travelling alone. He checked in at the Prabaramee Road resort on April 28 and was due to leave on May 6.
Phuketwan has his name but will not publish it until we can be sure relatives have been notified.
His body was taken to Patong Hospital.