Karl Joseph Kraus, who was arrested at his home near the city of Chiang Mai lured the girls to his home with imported chocolates and English lessons. One girl was only 5 when the abuse began. The sisters are now aged between 7 to 15.
Kraus who has been in Thailand for more than ten years approached the girl's family in 2008, offering to teach the kids English. He used to lure the children with sweets and he would ask them to perform sexual acts with them. He gave $120 for the elder sister recently instead of sweets for the deeds, informed police.
Police recovered around 100 photographs of naked children from his home, informed the police chief Kritapol Yeesakorn. Some photos portrayed him posing naked with other children. Police said that the investigations to identify them and contact their families are going on.
Police also said that they are probing whether he was a part of a pedophilia network, as many of the pictures were e-mailed overseas.
The parents noticed that the girls had lost interest in playing outside and inquired what was wrong with them. They took them to police who investigated and immediately sought an arrest warrant.