In all probability I will get a bus early morning from Chiang Khong to Chaing Rai . I dont really like arriving places in the evening so I think a night in Chiang Khong is probably the best idea.
Travelfish recently recommended Ben Guest House, 4/4 Chiang Mai-Lamphun Rd. Soi 2, A. Muang, Chiang Mai 50000 Tel. 053 244103
The plan is for one day and night in Chiang Rai then onwards to Bangkok the next day.
Some places I have heard are good arethe Gallery left hand side of the Wiangcome Hotel for the best breakfast and coffee and the Chay Naam next to the river for Thai food in the evening.