Christopher Paul Neil, 33, a teacher, was convicted of sexually abusing a 13-year-old boy after international police agency Interpol reconstructed a series of digitally 'swirled' Internet images of a man abusing boys.

Witnesses are scheduled to testify in the Thai Criminal Court this week as Neil is tried for sexually abusing the 9-year-old brother of his first victim.

He was jailed for over three years in August after confessing to molesting the older brother but has denied the charges in his second case.

Neil, originally from suburban Vancouver, was arrested after Interpol last year launched its first public appeal, seeking help in identifying the man seen in about 200 graphic online photographs abusing Asian boys.

The man in the pictures had created a digital swirl to hide his face but German computer experts were able to reconstruct the images.

The agency posted the suspect's picture on its website and appealed to the public for help, drawing more than 300 replies from around the world.

The operation was codenamed 'Vico' because the images were believed to have been taken in Vietnam and Cambodia in 2002 or 2003.

Child welfare advocates initially hailed Neil's arrest as a sign Thailand was working to overcome its sordid reputation as a haven for paedophiles and other fugitives.

But they said he should have received a tougher sentence to deter other paedophiles. -- AFP