Get the list of requirements from your local office, ask any questions of confusion here and then take all the correct paperwork to immigration once, a simple process.
Imagine how busy immigration offices would be if we all just went there to ask the same questions over and over, they’d be even happier to see us than they are now.
I think you're fine with a PGCE or a Masters, if in Ed. Apply online at Kru sapa, the Teacher's Council of Thailand. You could also go there, show them your qualifications and ask. They'll tell you what to do.