If you look at the US, there is a WalMart, but if you are in Thailand, there is a Big C with hundreds of consumer goods. Big C is the biggest local supercenter in Thailand with about 70 branches.
The biggest branch is located on the Rachadamri Road, which is one of the main streets in Bangkok. It is at a walking distance from both BTS Skytrain Siam Station and Chit Lom Station.
It is not just a supermarket, rather than it is the supercenter with Daiso, outlet, theaters, cafes and restaurants. You could find the matching clothes on the 1st floor, various kinds of fruits on the 2nd floor and well-known restaurants on the 3rd floor.
Before or after visiting the Big C, you can visit the Central World opposite with using a pedestrian bridge.