One person was injured after being cut by a shard of glass during the blaze, which erupted in an alley off Rama III Road.
It took firefighters about half an hour to contain the fire.
Prachak Tienkhunthod, a resident of the house where the fire is believed to have started, said that he had put out joss sticks before leaving his home to drive his wife to work in the morning.
He said he had left his electric fan and refrigerator plugged in but was unsure if a short circuit had occurred.
A neighbour, who declined to be identified, said smoke came out of Prachak’s house in the morning and expanded to two nearby wooden houses within five minutes.
No members of the three families living in the houses were at home during the fire, the neighbour said.
Yannawa District Office registered the families as fire victims for assistance.