Whenever a house is build, the spirits of the land are disturbed, so a spirithouse (san phra prom) is build for them, in an attempt to pacify the spirits so they will not haunt the house. Spirithouses are shrines in the shapes of houses, and may contain figurines.
Regular offers of incense, fruit, water, garlands, etc. are made to the spirits to please them and guarantee the safety of the house.
These spirithouses are very common, and just about every house/office has one.