I used to go to Bum rung rad for dental, ~ 10 years but switched to the Dental Hospital on Sukhumvit Soi 49. I switched, ~ 3 years ago, because of some dissatisfaction at Bumrungrad, and dozens of positive recommendations for the Dental Hospital.
I've only ever had a single crown done - I think it was 20,000 THB ~ 3 years ago. I was quite satisfied. My 6-month cleaning is 1,500 baht; I went a few weeks ago. I take a motorbike taxi from Thong Lor BTS, 30 baht. A lot of visiting friends, colleagues and Thai neighbors go there. They are very responsive, have a lab on site and have done emergency work for friends same day.
http://www.dentalhospitalbangkok.com/