I have this problem with eye doctors a lot here. Thailand is great if your eyesight is not too bad, but I have some major astigmatism problems that screw up many prescriptions. It has to be precise. Even back in the US, it was common for me to return a new pair of glasses to have the lenses remade.
Here, though, I have actually had an eye doctor at Bumrungrad Hospital, supposedly a top Western-style hospital, tell me flat-out that he did not believe I could not see out of the lenses he prescribed for me. I never could convince him otherwise. Did not go back to him, needless to say, and a complaint to the hospital was met with silence. (Bumrungrad is interested only in praise and generally will not act on complaints. I know quite a few people who have had a variety of problems with them.)
I now rely on a five-year-old pair. Maybe six years by now. I see okay, but it’s really a chore for me to get new glasses. For those with only mildly poor eyesight, Thailand is a bargain.