Update....I posted last week on our enquiry of moving from retirement visa to a non b visa.
After visit to Rayong Immigration the answer was that the person must return to home country and apply for a non b there. Then return to Thailand to join us as a teacher.
Obviously totally impractical and far too expensive with flights quarantine etc.
Shame about this as finding teachers has become a relatively impossible task now in Thailand. I am sure there are many retired expats who would be willing to help teach English but cannot do so on retirement visas ....
Thanks Tod Daniels for your advice in my original post.....