Bangkok has tons of markets. You can find cloth stalls almost every street here. So, if you ask me where to buy clothes in Bangkok, I would ask you back your budget first.
If you want a low-priced one, I would recommend you to check at the markets or the street stalls. You can find the clothes with less than 100 baht. And generally the more you buy, the more discounts you get. If you do not mind about budget, I would recommend you to go to the shopping malls where you can find many international brands.
Well, please bear in mind that both markets and shopping malls, you will usually see more clothing options available for women than men.
In the markets or street stalls
Clothes selling on street stalls or markets are similar. If you find the one that you like, you just bargain and buy it. If you feel like it is too expensive, do not buy it. Usually you will find the similar or exactly the same one on the next stalls. The big markets in Bangkok are Chatuchak Weekend Market and The Platinum fashion mall. The first market is an outdoor market, while the second one is an indoor market. You can buy either wholesale or retail at these two markets. Anyway, for some shops you will find a fabulous one that costs up to thousand baht.
In the shopping malls
International clothing brands such as Marks & Spencer, Esprit, Gap, G2000, Zara, Espada, Giordano, and so on are available in the shopping malls around Bangkok. The big shopping malls that you can find most brands are Siam Paragon, Central Chid Lom, and CentralWorld. Besides, in the shopping malls you will find local brand clothes which are usually cheaper, but gorgeous.
Have you ever bought clothes in Bangkok? Do you like them? Share it with me in the comment!