We mentioned it many times, get a visa that fits the purpose of your stay. The Visa Exempt and the tourist visa is not for long stay and to work to afford this stay.
The Non Immigrant ED visa is to sit in a classroom to study not to teach, but I understand, schools, directors, agencies and all those others does not make it easy.
For those in Chang Mai, times are changing at the moment, take care what ever you do:
Chiang Mai: Crackdown on tourists teaching at language institutes and cram schools
The post emphasizes the importance of obtaining the correct visa for your stay in Thailand, particularly warning against the misuse of Visa Exemptions and tourist visas. It specifically addresses the Non Immigrant ED visa, clarifying its intended use for studying rather than teaching. Additionally, it mentions a crackdown in Chiang Mai on tourists who teach at language institutes and cram schools.
The ask:thailand community, consisting of multiple Q/A groups with over 100,000 members, powers this platform. It is not an official government resource. Our members actively contribute to this resource, and while we strive for accuracy, we cannot guarantee its complete reliability. Assistance to travelers is provided as a community service.