About 4 months ago, I was diagnosed with bacterial pneumonia after going to the emergency department of Chiang Rai's government hospital. Four bedside visits by two doctors, both spoke excellent English.
OTOH, I broke my forearm in a scooter accident some time ago. A surgeon was very keen to pin and plate my arm, but only after waiting 48 hours for a medication to clear my body. I persuaded him to settle for a cast, my arm healed normally.
I agree the competence of doctors in Thailand is something of a lottery.
Unless it's an emergency, any surgery I have is done in Australia.