As part of an ancient civilization, the Thais have inherited beliefs in supernatural distribution of favours and afflictions to human beings. Animistic in nature, these beliefs are outside the realm of modern science. Some of the cults and creeds based on such beliefs can be thought of as a religion in an embryonic state, while others are seen to be void of any religious value whatsoever.

The origin of these beliefs can be traced to an attempt of the human mind to cope with the crises of everyday life … These painful questions entailed by life need to be explained in terms of concepts with which people feel comfortable. The existence of supernatural forces that hold sway over the order of the universe appears to be quite natural. The entities endowed with supernatural power are spirits, demigods, demons, deities, the sun and the moon. They are to be appeased, besought or pacified by sacrifices, prayers, rites, etc. The form and functions of the propitiation depend on the subject as well as on local peculiarities.

For this class of supernatural, only the spirits and deities need to be described here. The Thai idea of the spirit or the deity differs somewhat from that of the Indo-Europeans or Aryans. The Greeks assign to each natural force, or quality, a deity — the God of the Wind, the Goddess of Beauty, and so on. Each deity has its own genealogy and function. In Thai folklore, however, a spirit or a deity is born out of the soul of a departed human being. Consequently, there is no clear distinction between spirit and deity.

There are a number of Thai deities which are accorded high official titles and functions, those such as Phraya Yomraj, a deity which regulates the social conduct of Thai citizens; Phra Sayam Devathiraj, a deity which guards the Kingdom of Siam; Phra Sua Muang, a deity which protects the city; Phra Phum Chao Thi, a spirit which looks after a place of residence; Chao Pa, a spirit which rules a forest; and Chao Smut, a spirit which lords over the sea.

The spirits of some departed celebrities are also worshipped by the Thais. Included in this category are the spirit of Chao Po Krom Luang Chumporn (male), the spirits of Chao Mae Tubtim (female), and the like. Some spirits derive their names from their abodes, such as Chao Mae Khao Sam Muk, which is a female spirit named after the hill on which it resides.

Mention must also be made of the panoply of spirits revered by the Thais of the Northeast. Phya Thaen is a spirit which rules the sky and gives rain at the right time of year. It is also a spirit associated with the fertility of crops. Phi Baan or Phi Poo Ta is the spirit of an elderly member of the family. It looks after the well being of the village and its dwellers. Phi Chua is also the spirit of a departed member of the family. Instead of being reborn, it chooses to stay in the land of the living to protect its offspring. Phi Chua is offended by improper behaviour on the part of children and pleased by offers of incense and merit making. Phi Pob is a malevolent spirit, which feeds on the kidneys and other entrails of the body in which it resides. Without proper exorcism, the host body is bound to waste away to eventual death. Phi Pao is the spirit of an uncreated corpse. The spirit feeds on liver and raw flesh. Tao Jam is a spirit, which guards the shrine of Poo Ta, an elderly spirit. Phi Fah is the spirit which possesses the body of an exorcist during the act of exorcising or healing. Moh Tham is the spirit of a departed religious man. A medium possessed by the spirit of Moh Tham is supposedly endowed with the power of magical healing.

In the northern part of Thailand, some spirits are similar to those in the Northeast, but they are often known by different names.

Thao Thang Si (the four spirits) guard the four corners of the world. They are worshipped on the traditional New Year’s Day and on occasions when a favour in the form of family prosperity is sought. Phi Baan and Phi Muang are the spirits which protect a village and a city, respectively. Phi Sua Baan is another name for Phi Baan. A Phi Sua Wat, which protects a temple, is also spoken of. The northern people have a town-blessing ritual tradition in which Phi Baan Phi Muang is beseeched to bless the town with prosperity and good crops.

Poo Thaen, Ya Thaen or the spirits of Grandfather Thaen and Grandmother Thaen, are the spirits of the first man and woman who inhabit the earth. In Thai folklore, everybody is a descendant of Poo Thaen and Ya Thaen. Phi Nang Mai is the spirit which resides in the forest. This spirit brings illness. Phi Pong Sua is the spirit which can enter the human body and feed on blood.

One of the best-known spirits worshipped by the Thais in the central plain area is the spirit of Phra Phum Chao Thi. There are altogether nine subjects, which the spirit of Phra Phum Chao Thi looks after. All of them have to do with the land or those which stand on the land, i.e. house, door and top of the stairs, wedding house, animal enclosure, barn, rice field, orchard, threshing patch and temple ground.