The Chiang Mai night market is unforgettable.
Chiang Mai's famous Night Bazaar is a shopping paradise in the center of city. Vendors set up stalls along the main street as the sun sets, but side alleys, side streets, and buildings along the road also are open and full of stands loaded with merchandise as well. Knockoffs are everywhere, and inexpensive fashion is a staple of the market. You can find handmade items for a fraction of what you'd pay in the US.
The market can be a bit overwhelming and touristy — I had some major sensory overload throughout the several hours it took me to cover as much of the market as I could — but the hustle and bustle, the sights and smells, and the overall atmosphere of the market was an experience I loved and will never forget.