The suspect was named as Kiattichai Cha-em, alias "Professor Phet the disciple of Luang Por Nen", aged 25.
One of the suspect's customers, Ploi, a 27-year-old woman whose real name was withheld, told investigators the fortune teller chanted spells and rubbed oil all over her body during the 30-minute ritual.
"Just think that your boyfriend is performing the ritual and I'm not the one doing this because I'm just a vessel. So if you feel that I'm taking advantage of you, please forgive me," Ploi quoted him as saying.
She alleged Mr Kittichai also threatened her, warning that if she told anyone about the ritual she would face her demise.
The woman told police that she eventually decided to take legal action against the fortune teller because she felt that she was being sexually abused by him.
She said she believed that his other female clients may be afraid to complain to police.
Mr Kiattichai was later arrested at his workplace in Chon Buri's Muang district. Mr Kittichai looked stunned and cried, claiming that he did not sexually abuse his clients, police said.
He denied the charge, saying he had no intention to harrass his clients.
"My body was a vessel during the rituals, and I only used a mahaniyom (popular-boosting) oil on them," the suspect said.
Police did not believe him and he was detained for further questioning.