Can I obtain a Muay Thai ED Visa for my first year in Thailand, and can it be extended by switching schools?

ED Visa Question: I was thinking of getting a Muay Thai ED Visa for my first year and try Thailand for about a year to be sure that I want to retire in Thailand.

Do most of the Muay Thai Schools offer ED Visa, would I have to leave the country and then apply for the ED Visa once I find a good school and can the ED visa be more than one year?

I've heard that people stay in Thailand on ED visa for years by switching to different types of Schools. Like from Language School to Muay Thai to Yoga etc. Is that possible?