Singapore - Three young Britons pleaded guilty on Monday to sexually assaulting a drunken Malaysian woman during a stag party in Singapore and may now face long prison terms and caning.Khong Tam Thanh, Le Michael and Vu Thai Son, all in their 20s, were originally charged with rape but admitted the lesser offence of sexual assault at the city-state's High Court after a four-day trial.The men, British citizens of Vietnamese origin, will be sentenced on Tuesday. Sexual assault carries a penalty of up to 10 years jail and caning, a punishment that dates back to British colonial rule.The three were in Singapore in September as part of a group of nine for a bachelor party, and attended an electronic music festival called Ultra Singapore.The groom, the brother of Khong, was also on the trip.They met the 23-year-old woman in a popular nightspot in the city-state. After she had agreed to have sex with one of their friends, a British citizen also of Vietnamese origin identified as Richard Ahn, he took her to his hotel room. After the pair had sex, Khong, 22, Le and Vu - both 24 - took turns to enter the room and have sex with the woman as she lay drunk and unconscious, the court heard.While the men took care to make as little noise as possible, the woman woke up as Le was assaulting her. Prosecutors asked for a prison sentence of between five and seven years. "The offender must pay for what he has done... (In this case), they clearly exploited the victim," said deputy public prosecutor G. Kannan.Khong and Vu, who worked as beauticians in Britain, were convicted of an additional charge of sexual assault by using their fingers to penetrate the woman. Le is unemployed.The men's lawyers all read out letters from their clients apologising to the victim. "(Khong) was rash, he was reckless, and now he regrets it," his lawyer Shashi Nathan told the court. He also offered the victim $3 700 in compensation, which prosecutors said the woman has accepted.