It's not exactly your typical tourist attraction, but Chiang Rai's central market can be a very interesting place to look around. It extends for several blocks near Wat Phra Singh, both outdoors and under cover.
The many varieties of dried chilies (and tobacco) available in the covered market.
The outdoor parts sell mostly fresh fruits and vegetables. These stalls often spill out onto the sidewalks around the market.
Fresh vegetables and fruits in the market.
Inside you'll find all manner of dry goods, including clothes, pots, pans, spices, etc. A good example is the stall pictured at the top f the page, with several types of dried chilies on offer, as well as garlic, shallots and tobacco.
A second fresh market can be found near the bus station and night bazaar area. This market has several flower stalls on the north side that can be interesting.