The interior of the main viharn seems to house beautifully colored paintings and a golden seated Buddha. I say seems to because the 2 times I went there the doors were closed. To the left of the white hall, there is another hall with access to the toilet. It's rare that I recommend it, but go to the toilet, you will probably be amazed by the beauty of the place and at first think that it is a wing of the temple but no, it is the toilet. I also advise you to come back at night, to see the beautiful lightening of the temple.
Wat Chiang Rai is a temple and when you visit a temple in Thailand there are some rules to know and follow :