Can I bring my parents as dependents to Thailand on an Ed visa or work visa?

Those are what you need to ask your school or employer.

For Non-ED based on studying, if you are studying full curriculum at a university, parents over 50 MIGHT be able to get Non-O dependent. But you have to talk with the university first if they can provide the necessary documents for your parents. Parents cannot get Non-O dependent if you are on Non-ED from other private schools such as language schools.

For Non-B based on employment, it is totally up to your employer's company policy. It'd be possible if the employer agreed to provide documents for the parents over 50 to get Non-O dependent.

I approved this post to provide basic information. This is a type of post we usually decline because that question can be answered only by your school or employer, and depends on how they do with the local immigration office.