Is it possible to convert a Non-b visa to an Ed-Visa without having to leave the country? I won't longer teach in my current school and since I'll be soon job hunting, I'm thinking to master my Thai for some time, untill the situation is back to normality.
TLDR : Answer Summary
The possibility of converting a Non-B visa to an Ed-Visa without leaving Thailand is generally not allowed. While you may need to cancel your current Work Permit and inform immigration about the cancellation of your extension of stay, the common procedure has been to exit the country to apply for a new visa. However, under current circumstances, it may be worth checking with your language school and immigration if there's an option for a direct application based on study.