What is the renewal process and timeline for a Non-B visa in Thailand?

When the Non Immigrant B visa is stamped in your passport you also get 90 days to stay inside Thailand. After 60 days you return to the Immigration Office with document of your employer and apply for the 1 year Extension of Stay based on Employment.

And 30 days before that years ends you visit Immigration again with documents and apply for a new 1 year Extension of Stay and keep on doing this as long as you work for this school.

If you need to travel, you apply for or a Single or a Multiple Re-Entry Permit.

You can do this directly after the Immigration Officer stamped the 1 year Extension of Stay inside the passport.

What do you mean by "had my non-b approved"? Do you have your first Non-B visa stamp (1-page stamp) and 'permitted until xxx' stamp (small rectangle stamp with date) in your passport? Or do you mean your work permit or ...?

When every requirement including your work permit application is met, you are stamped for the first 90 days from your in-country visa. When you have less than 30 days from this 90-day stamp, you get another round of documents from your employer/school, go to the immigration office again and apply for a 1-year extension based on teaching. This 30-day window is the same time of the following year, every year.

If your first in-country visa is issued in July, your 1-year extension application is in September-October every year after.