Police said he lured his victims to his house for a daytime ritual, where he would then feed them drinks mixed with potassium cyanide and a sedative.
Police also detained an accomplice who was promoting money multiplying services on social media. However Tohari said he had largely acted alone.
Experts told the BBC that money multiplying scams are common in Indonesia, with many social media posts advertising such services.
They have been successful because community beliefs in the occult remain strong in the country.
Sociologist Imam Prasodjo of the University of Indonesia told the BBC that it takes time to educate people about these scams, and that police must act more quickly against them.