Khong Tam Thanh, Le Michael(pictured above) and Vu Thai Son were originally charged with rape but admitted sexual assault following a trial.
The attack happened after the three visited Zouk nightclub in Singapore.
The victim aged 23, had returned to the Carlton Hotel with a fourth man who was a friend of the trio and had consensual sex.
Thanh, 22, Michael Le, 24, and Thai Son, 24, took it turns to enter the hotel room and sexually assault the woman while she was unconscious,Associated Press reports.
She only realised what was happening as Michael Le was assaulting her and reported the attack to police in September last year.
Thanh has been jailed for six year and eight strokes of a cane.
Thai Son faces six-and-a-half years in prison and eight strokes of the cane.
Michael Le was sentenced to five-and-a-half years in jail and five strokes of the cane.
