Hard to suggest anything without knowing anything about you or what you like to do.
Personally I'd go and stay around Phayao lake for a night and hike up Doi Nok.
Depending on why you're going to Chiang Rai and where to next, maybe consider going by bus to Chiang Dao, stay near the cave (I like Malee Nature Bungalows) then onward to Thaton where you can get a river boat to Chiang Rai. Also a few good highlights in between or beyond such as Mae Salong and Doi Tung, or Chiang Saen on the Mekong riverside. Anyway see the map.. https://goo.gl/maps/8NHxqzVMkYx