Mader left Thailand on Monday for Vietnam before flying to Canada , he said.
"We have asked Canadian authorities to extradite him because he has committed crimes in Thailand ," Apichart said.
Police issued an arrest warrant for Mader on Wednesday after an 8-year-old Thai boy said he was taken to Mader's hotel room by a Thai man in the beach town of Pattaya . The child alleged he performed oral sex on Mader, Apichart said.
Police said they believe Mader abused at least three other boys.
Mader's case comes hard on the heels of arrests of other alleged sex offenders, highlighting the lure of Southeast Asia as a magnet for sexual predators.
Cambodian police arrested a German man Thursday after raiding his Phnom Penh hotel room and catching him in bed with a 14-year-old girl, said Keo Thea, deputy chief of Cambodia 's anti-human-trafficking police. The man was identified as a 61-year-old from Cologne. The girl told police she and the man had sex on several earlier occasions.
The German man was arrested for debauchery - a Cambodian legal term for the sexual abuse of children under the age of 16 - a charge that is punishable by up to 20 years in jail.
Several Southeast Asian countries, including Thailand, Cambodia and Vietnam , are popular with pedophiles because of lax law enforcement, corruption in the justice system and poverty that forces children into prostitution.
Thai and Cambodian police were coordinating on Mader's case, Apichart said.
Mader was arrested in Cambodia in 2004 for allegedly abusing five boys there, all under the age of 15, said Samleang Seila, the director of French child rights group Action Pour Les Enfants.
But a Phnom Penh Municipal Court set Mader free because of a lack of evidence, he said.
The problem of Western pedophiles was spotlighted anew with the Oct. 19 arrest of Christopher Paul Neil of Canada, who is accused of having abused Thai, Vietnamese and Cambodian boys.
Thai police captured Neil after Interpol launched an unprecedented worldwide appeal to find him.
The hunt for Neil began three years ago when German police discovered about 200 online photographs of a man sexually abusing children. His face was digitally obscured, but German police were able to unscramble the photos, which were then circulated by Interpol. Public tip-offs helped police identify Neil as a suspect and he was arrested in rural Thailand.
Neil has been charged with child sexual abuse and is in police custody in Thailand .
Neil worked as a teacher in Asia , as has Paul Cornelius Jones, 39, a Briton arrested Tuesday after police raided his Bangkok apartment and found a computer containing photos of naked boys and girls.
Jones, of Cardiff, Wales, has been charged with distributing pornographic photographs of children under age 15, which carries a maximum penalty of 15 years in prison, Apichart said.