Police said the fire started at the 6 units of shophouses on Ratchaprarop Road near Chaimongkol market at 5.10am.
Firefighters had a tough time reaching the site as the shophouses are located on a small soi, but they managed to put out the blaze by 7am.
Police said the fire started on the first floor of a garment shop and spread to other floors and units very fast.
Thick smoke prompted police to close traffic from the Ratchaprarop intersection to the Pratunam intersection.