There are four kinds of spirit house seen around Bangkok, the most common being the 'San Jao Tii' and 'San Pra Phoom', which often appear together in pairs. Most are made of auspicious wood and resemble a traditional Thai house or temple, though increasingly in downtown Bangkok and beyond spirit houses are cast in concrete or stone and sport hi-tech designs. They often have foreign architectural accents, like Chinese gables or Khmer-style prangs (pointed spire).
Their colours are usually linked to the astrological chart of the landowner, but, if they're Thai-Chinese, it's not uncommon to find them clad in lucky red and gold. All are habitually decked with offerings of food, incense, candles and flowers - gifts for attendant spirits.
1. San Jao Tii
The 'San Jao Tii' is for the lord spirits who inhabit the land. They typically have four pillars ground into the earth, and resemble an old wooden Thai house. Originating earlier than other kinds of spirit house, these embody indigenous animistic beliefs, the idea that invisible forces and spirits shape material reality. The landowner's relationship with them thus mirrors the mutually beneficial animistic tradition: the 'land god if we look after you and give you shelter, please look after us' philosophy.
Its attendant land lords are usually represented by figurines of an old man and woman placed inside, and offerings like angels, dancers, elephants and horses included to entertain them. As ordinary animistic spirits occupy everyday material things - everything from rice fields, barns, temples, trees, bridges and gates - as well as humans, these kinds of spirit houses are places to appease the spirits rather than revere them. Expressions of devotion are reserved for celestial beings or Lord Buddha.
2. San Pra Phoom
A 'San Pra Phoom' is a home for the guardian angel or spirit which inhabits the land. Mounted on a pedestal, it usually resembles a Thai Buddhist temple and is crowned by a Khmer style prang. The most popular kind, the 'San Pra Phoom' is not immune to city living trends and fads - those in downtown Bangkok come in all kinds of styles and materials, from modernist to sleek to hi-tech, if not wood, then concrete, stone or glass.
It evolved from the 'San Jao Tii' (shrines for lowlier land spirits), when Hindu and Buddhist influences began filtering into Siam around the turn of the 1st Century. The single pillar is said to represent Mount Meru, the sacred mountain in Hindu and Buddhist ideology where gods reside. To reflect the hierarchal nature of the Hindu cosmos (which is absent from animism) it therefore stands higher, and prouder, than the 'San Jao Tii'.
A figurine representing the guardian angel of the land usually appears inside. This is an image of Phra Chai Mongkon, a Hindu angel with sword in one hand and money bag in the other. He, it is believed, will look over and guard the property and its inhabitants. More often than not, a motley crew of attendants and animals accompany him. Unlike the 'San Jao Tii', this breed of spirit house represents the Thais' belief in forces higher than themselves, a cosmological hierarchy (though for Thais, unlike Hindus, the enlightened Lord Buddha surpasses all Gods). Therefore, aside from making offerings to the guardian angels, people may pray for help at a 'San Pra Phoom', and sometimes invoke Buddhist chants.
3. San Phra Brahm
This larger open-sided spirit house, often found outside big homes and offices, is the abode of the Hindu deity Phra Brahma, the God of Creation. If, after he has been invited to occupy it, it gains a reputation for being especially auspicious it may become a shrine, people flocking to pay respect to Brahma's divine grace and request help in their everyday lives (see Erawan Shrine). Each of its four open sides reveals one of the four faces of the statue inside, each in turn representing the virtues of kindness, mercy, sympathy and impartiality.
4. San Piyanda
This is a temporary spirit house, with a simple form. It's especially important for Thais to recognize land gods when building, to ensure the workers are kept safe, and so this does the job until a permanent one can be erected. Making merit at a temporary spirit house, or existing one, on construction sites is often thought a better guarantee of personal safety than the hardhat.