It is believed that the spirit (or phi) has supernatural power and that there are various kinds of spirit who need to be respected. If the spirit is mistreated, it will cause illnesses among people. Among the different kinds of spirit is Phi Fa, who is the most powerful and can treat ailing patients. Lam Phi Fa is a ritual of treating mentally disordered patients or those suffering from psychosomatic illnesses. This ritual also unites all the family members and makes them think whether they have done anything indecent.

The medium or kru-ba arranges offerings for spirits, and studies the illness, its causes and severity. If the illness is a result of a minor mistreatment by the patient of a particular spirit, that spirit will be invited to accept an apology, which is usually accompanied by an offer to follow the spirits wishes. This part of the ritual is called Lam Song.However, if the illness is serious, Phi Fa will be invited to treat the patient. The musician will play his wind instrument called kaen while the kru-ba dances to invite Phi Fa, while walking around the offering. So do the assistants to the kru-ba. Upon the descent of Phi Fa, everyone will unconsciously shake and lose their consciousness. Phi Fa will give them the idea of how to treat the patient and then leave for heaven. This ritual is there fore called Lam Phi Fa.