The fire broke out at about 8am and was brought under control about half and hour late, although firefighters were still battling the blaze on the third floor of the building on Ratchadapisek Road.
Billows of smoke were seen coming out from the building.
Firefighters entered the building at about 8.35am and did not find anyone trapped inside.
The cause of the fire is being assessed.
The incident caused traffic snarls as several lanes in front of the mall were blocked for fire-fighting operation.
Video from JS100 Radio homepage