Police and rescue workers arrived at the scene, a hotel on Rat Uthit 200 Pi Rd near the end of Soi Bangla, to find the man found unconscious and lying face down with serious head injuries. Blood was visible at the scene.
Emergency responders from Kusoldharm Foundation Phuket and Patong Hospital attempted CPR and rushed him to hospital, but he was later pronounced dead.
Police believe the Australian, from Cottesloe, Western Australia, fell after losing his balance while climbing the stairs to the third floor.
According to police, the man had returned to the hotel with his wife shortly after 1am following a night out drinking. Witnesses said the couple had passed the hotel reception before a loud noise was heard moments later.
The wife told investigators that her husband appeared unsteady on his feet and fell backward down the stairs from the second floor as they returned to their room.
Officers interviewed hotel staff and are reviewing CCTV footage to confirm the events leading up to the fall.
No foul play is currently suspected. Officers are continuing their investigation, police said.