In Sukhumvit Soi 19 not far from the Honey Hotel there is good "Dental Spa", well managed by a Thai lady Dr. Watchareewon 'Lily' Porncharoen.
www.bangkokdentalspa.com/thepress.html
www.dentistbangkok.net/dentalbangkokthailand/bangkokdentalspa/index.html