Hang with the Cool Kids at Saphan Phut Market
Saphan Phut (memorial bridge) market is the alternative to the tourist obliterated markets of Bangkok. The crowd here is 100% locals and teenagers, and it makes for some great people watching.
I had my tarot cards read here in enthusiastic if not entirely fluent English, and the experience was, to say the least, unique.
You can pick up everything from vintage T-shirts to computer memory sticks shaped like Ice Cream or Mini Mouse. Food stalls are set out along the way, too, so you can snack and shop. The market is open 8pm to midnight every evening.