It is not only the largest market in Thailand; in fact it is the World's largest weekend market. Around 200,000 visitors come here everyday (although most stalls remain open only on Saturday and Sunday). You can find local handicrafts, delicacies (even live animals!), to clothes etc. on its 15,000 stalls located here. A shopper's dream, you can literally send hours here!
This markets sells pretty much everything. No really, you can find pretty much anything here. Chatuchak is a massive maze of stalls, so you may want to avoid splitting up; unless you’re with someone who knows the market well. I’ve been utterly lost in this market before.