A Brisbane soldier is fighting for his life in hospital after being assaulted on Queensland's Gold Coast on Sunday.

Private Joe Arnold, 22, from the 6RAR at Enoggera barracks in Brisbane, was attacked by three men while he was on leave in Surfers Paradise.

The soldier, who has survived tours in the Middle East and East Timor, is now in hospital on life support.

Detective Inspector Tim Trezise says at about 3:00am (AEST) on Sunday, a passerby saw one of the men punch Private Arnold who fell and hit his head on the ground.

"He's on life support at the moment - he's not regained consciousness since this incident," he said.

A major incident room has been set up and homicide detectives have joined the case.

Police say they are investigating whether the same three men bashed a Victorian tourist 30 minutes earlier after asking him for money.

He escaped with minor cuts and bruises.