Judge Yeth Molin also ordered Ian Paul Bower, 46, to be deported back to Britain upon completion of his sentence. He will also owe $2,500 in compensation to each of his victims, the Phnom Penh Post reported.
Bower was convicted in 2001 in a British court for sexually abusing a 10-year-old boy, for which he served one year and six months in prison.
Bower was charged with sexual assault of two boys in 2007 in Cambodia, however, the charges were dropped after the young brothers rescinded their statements.
He has remained free in Cambodia since 2007, and has worked as an English teacher for the Cambodian Air Traffic Service.
Bower's lawyer said his client has appealed the sentence.