The robbery took place Monday morning at the Aurora gold shop in the Navanakhon branch of Tesco Lotus in Khlong Luang district.
Staff member Kannikar Rattanathaisong, said robbers wearing masks threatened her and three other staff with a gun and forced them to hand over the gold.
Pol Maj Gen Samit Mukdasanit, chief of Pathum Thani police, said the robbers made off with about 134 baht gold weight, worth around 2.5 million baht.
He said shop staff were unhelpful and refused to allow the police to view footage from the shop's surveillance cameras.
He said police reviewed footage from surveillance cameras from other stores in the hypermarket to identify the suspects.
He said there were three of them _ two men and one woman, who asked shoppers about the super-store's exits before they struck.