An Australian man who died after a bar fight in Thailand had been choking a waitress shortly before an American man punched him, police said.

Benjamin Robb, from Newport in Victoria, became involved in a drunken brawl at the Ruby Club in Pattaya, 150 kilometres south-east of Bangkok, last Friday evening.

Pattaya police captain Sombat Kaewpoonmuk said 42-year-old Mr Robb was drunk and behaving aggressively, holding a waitress up by the neck until her feet lifted off the ground and her face turned blue.

An American man, Jose Manuel Polanco Jr, told police he punched the Australian several times, saying it was in self-defence.

Mr Robb sustained major injuries to his head and upper body before being knocked unconscious. He was reported to have been thrown across the bar and later sustained repeated kicks to the head and body.

Thai paramedics and police were quickly on the scene and Mr Robb was taken to the nearby Pattaya Memorial Hospital.

Despite treatment he died in the early hours of Saturday from his injuries, including internal bleeding.

Eyewitnesses said both men had been drinking heavily in the afternoon and appeared intoxicated when the fighting broke out.

The Ruby Club said in a statement the altercation had been brief and had left the Australian unconscious.

Mr Polanco Jr is in custody while Thai police investigate further.

The Department of Foreign Affairs and Trade said it was providing consular assistance to the man's family, and that it was unable to provide further details for privacy reasons.

ABC/AAP