It is a characteristic feature of Thai architecture that walls and columns taper towards the top. The walls are very thick, with deep door aid window embrasures. Beautifully carved door and window surrounds set off the pure white of the walls. Doors and shutters are or carved wood, lacquered in black and gold, painted or inlaid with mother-of-pearl. The interior walls are covered with mythological scenes and the ceilings are decorated. Opposite the entrance, usually in front of the west wall, is the most venerated Buddha image. In front of the figure is an altar consisting of several tables for offerings, mostly garlands of flowers. Statuettes of the Buddha, vases, lamps, clocks, miniature chedis (reliquaries) and jars of sand, in which lighted incense sticks are set, are scattered about in a random fashion which to western eyes seems to detract from the dignity of the Buddha. Shoes must be taken off before entering the Wat.

A series of roofs set one above the other, covered with brilliant glazed tiles, give a Thai temple its characteristic silhouette. The ends of the beams in all royal and religious buildings have a curious ornament called the cho fa, the origin of which is unknown. The gutters are decorated with stylised nagas (snakes or dragons) of gilded wood. Sometimes there are small bells with small heart-shaped pieces of metal attached to their tongues, causing them to tinkle in the wind. Bells of this kind hanging from coloured ribbons are often sold as souvenirs, particularly in Wat Arun and Wat Phra Keo.

The most important rituals of monastic life (ordinations, etc.) are performed in the Wat. The sacred area is marked out by eight boundary stones (sema). Originally these were flat stone tablets with carved decoration, lance-shaped, with a Gothic style pointed arch at the top, slightly curved sides and a horizontal base. Stones of this kind were also set up on town or palace walls like battlements. When they mark the boundaries of a bot there are often snake heads on either side of the base. In order to protect the stones from the weather little houses or tabernacles are set over them, richly decorated and crowned by various spires and structures, and often by a phra chedi. In this way the efficacy of the sema in warding off malign influences is doubled, since chedis also serve as boundary marks (for example at the national frontiers). In many parts of the country, particularly in the north, women are not admitted to the sacred area.