If you have some more time to be out of central Bangkok, there are plenty places where you can shop. One of the shops is Union Mall.
Union Mall is 3 stories building with many restaurants and entertainments such as arcade. This place is very well-known among locals for clothes shopping. Their clothes are very various as almost as JJ Market, and the price is also very reasonable. There are many shoes stores and clothes stores, and you can also but some electric stuff in there as well.
Union Mall can be reached by MRT Pahonlythin station.
