Trafficking official says man, 62, investigated in Sweden for child sex offences in 1981.
PHNOM Penh's municipal court has charged a 62-year-old Swedish national with sexual offences against minors.
Johan Abrahim Escori faces 10 years in jail if convicted.
Keo Thea, the municipality's director of anti-human trafficking and juvenile protection, said Escori faces two charges of committing indecent acts and sexual intercourse with three underage boys.
Escori was arrested at the Angkor International Hotel in Phnom Penh on Wednesday, where he was sharing a room with a 9-year-old Cambodian boy whom Escori claimed is his adopted son, Keo Thea said.
"I have been told the suspect is in pretrial detention with two charges against him of committing indecent acts and sexual intercourse with minors," Keo Thea said.
He said Escori had been accused in 1981 of child sex offences in Sweden but was not jailed due to a lack of evidence. He added that Escori was suspected of committing crimes against the three boys in Cambodia since late 2006.
Samleang Seila, the country director for the French child protection NGO Action Pour Les Enfants, said the man had lived with five boys prior to his arrest.
Samleang Seila said APLE had been watching the Sihanoukville resident since 2007 after noticing he was regularly accompanied by boys to restaurants. He said Escori had been questioned by local police in late 2007 but released.
Samleang Seila said Escori applied last year to adopt the boy but was denied because the proper authorities had not approved it.
"The man filled out a form asking the mother of the 9-year-old boy whom he liked most to be his adopted son," Samleang Seila said, adding that this tactic had been used by other foreigners. "His mother agreed in exchange for US$500 to prevent police and local NGOs from getting suspicious."