I like Bangkok Christian Hospital. For other people in the future I would also suggest Pulse Clinic on Silom. Worth looking at all their services. For anyone short of cash most pharmacies will sell amoxicillin without prescription very cheaply, just asking for a reason, like a sore throat.
I have also used BNH on Convent, not far away, many times for minor medical issues and been happy with good service at a reasonable price.