The fire started on the first floor of the three-storey, two-unit shophouse building of Chokechai Furniture shop on Sri Suthat Road in Talad Yai sub-district of Muang Phuket district at about 1.45am.
The blaze then expanded to upper floors of the building. It took firefighters with about 10 fire engines several hours to put out the flames. The shop stored both wooden and plastic furniture and home decorations.
They found inside three bodies of the same family holding one another — Mongkol Ruanchai, 45, his wife Nucharee, 42, and their son Theerawat, 9.
The other was Chatcha Kanpat, 32, who was found dead near a window of the same bedroom. The injured was Janhom Jakkaew, the 51-year-old owner of the shop. She was sent to Vachira Phuket Hospital.
Miss Janhom, whose legs and arms were broken, said they were sleeping on the third floor when the smoke woke her up. When she tried to wake the others, thick smoke blinded her, forcing her to jump down.
Police assumed the fire resulted from a short circuit. The damage was reportedly estimated at about seven million baht.