Been having all my dental work done in Bangkok for the past 15 years. Never had a problem at all. The work has always been if a very high standard. I use a place off Siam Square - but a little research will find you a very good place. Prices are very cheap compared to say the U.K.
There is a place that I’ve walked past at Thong Lor a few times, on Soi 55. It looks the absolute business ! Porches and Bentleys parked outside etc. I had a quick look at their ‘lead’ prices, and even there they were cheap compared to the U.K. Think if I needed major works I might head that way.