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. Tha market is open 8pm - Midnight every evening.