The 22-year-old woman had been at a party at the Waikiki Beach Club in Sihanoukville on Monday night where the two men lived and worked as waiters, The Cambodia Daily reported.

Sarith Sethy, 22, and Kuoy Pov, 17, allegedly found her asleep on O'Chheuteal Beach in front of the club and took her back to their room and each raped her.

The resort workers confessed after their arrest on Wednesday.

Provincial serious crimes bureau chief Nhet Phoan said the men told police they were unable to control themselves.

"They raped her because they couldn't control their feelings when they saw her sleeping alone on the beach," he said.

"When they saw the victim drunk and sleeping on the beach alone, Mr Sethy brought her to their room and raped her with his friend.

"The older man confessed to raping her two times, and the younger man to raping her only one time."

The two men were charged with rape on Thursday.

A spokesman for the Australian Embassy in Cambodia said it was ready to provide assistance to the woman.

"We are aware of reports of the alleged rape of an Australian woman in Sihanoukville earlier this week and stand ready to provide consular assistance," he said.

Daily flights to Sihanoukville have made it a popular destination for backpackers.

O'Chheuteal Beach, known as Serendipity Beach, has become a party zone, lined with restaurants, bars and accommodation.