Chiang Rai has a number of good ones.

Little Duck
They started it all .. the lunch buffet trend in Chiang Rai, that is. Little Duck Hotel is located near the 'Y' intersection south of town center, where Paholyothin and the Superhighway divide. Their original buffet lunch was Bt 80 and you had to arrive early.

Tables became scarce quickly and the supply of food dwindled as well.

At last check, the price was Bt 120. Certainly worth a try.

Rimkok Resort
Transportation is required to get to the Rimkok. But it's worth the trip for their daily lunch buffet. Each day from 11:00 to 14:00, Rimkok lays out a sumptuous all-you-can-eat buffet of Thai and westernized dishes. Noodles and desert tables ar available as well.

This entire experience will set you back about Bt 120 unless you order something ala carte. Beer is expensive.

Rumors say that the dinner buffet, served from 18:00 to 22:00 has an even greater variety and costs about Bt 200. At dinner you get some entertainment as well.

Rimkok offers a special bonus as the grounds are quite appealing. A walk along the rive is an excellent after lunch or dinner exercise.

Wiang Inn
For convenience and quality, try the dining room at Wiang Inn, located on Paholyothin Road. It's a bit more formal than the Rimkok, but the fare is excellent. Thai and western food plus desserts for Bt 125.

Inn Come
Located between Paholyothin Road and the Super Highway on Rat Bamrung (about 5-6 km south of the main intersection). They have a large dining room and lots of Thai customers. That should give you a hint. Priced at Bt 120.