Phuket City Municipality firefighters were called to the three-storey commercial building, located near the Lan Nawamin public area on Phuket Rd, at about 10:30pm.
Firefighters arrived to find the back of the building covered with flames.
The fire teams took just 15 minutes to douse the fire, and confirmed that no people were injured in the incident.
The fire had damaged two units at the shophouse building. The cost of the damage caused by the fire has yet to be estimated.
Local residents explained that no people were known to be living in the building, which was reported to be owned by the Apiwattatorn Co Ltd. The local residents said they believed the building was for sale.
However, local residents also reported that a homeless man had been seen regularly using the back of the building as a shelter, where he was protected from wind and rain on three sides.
It is believed that the man, estimated to be 55-60 years old, may have inadvertently started the fire by leaving a candle or lit incense unattended.
Officials are continuing their efforts to locate the man for questioning.