Chiang Rai's Cultural Hall Museum is a small local-history museum with displays on prehistoric tools, old weapons, pottery, costume, and Lanna writing. The exhibits are modest, but they help explain the city's place in northern Thai culture before you head out to the temples and larger art spaces.
It works best as a short orientation stop near the centre. Travellers who like local museums will get more from it than visitors looking for a polished national-level collection.