Firefighters arrived at the four-storey building in the Phoonpon shopping area to find smoke billowing out of the ground level and the top floor.
Firefighters took 20 minutes to douse the fire.
“At this stage we believe the fire started on the first floor (ground level), where many materials were kept. This made the fire spread very quickly Everything on that floor was destroyed,” said Capt Ronnaphum Permpoon of the Phuket City Police.
“Forensic police will investigate the scene to determine the cause of the fire,” he added.
Shop owner Kanokwan Uthaipan, 50, told officers, “The shop was closed when the fire started as I went to see the doctor with my husband. I received a call about the fire and so I came rushing back.
“The total cost of the damage would be not less than B2mn,” Ms Kanokwan added.