@Jaymie *******
Yes, it's possible. It's called changing the reason for a long-term extension. For example, I changed from a Non-ED (which is a specialized version of a Non-O) for purpose of education to a Non-O for purpose of retirement. Can be done, but you need to discuss with your local immigration office how. In my case, I had to have my school write a letter that I would complete my study on a certain date and ask immigration to terminate my extension of stay for purpose of education on that date. I was then able to apply to change the purpose of my extension of stay to retirement and needed to show that I met all the financial and other requirements (for example, being age 50 or older) as of the date of the application. When they granted my request to change the reason for my extension they put a one-line statement in my passport saying the purpose of my extension was now retirement (in Thai). They asked me how much I wanted to pay them for this change in purpose and I said 2,000 baht. I guess it is technically price-less but 2,000 baht was a great bargain as I did not have to leave the country to do this. I was quite happy. By the way, I continued to attend language classes, the letter from the school is just to allow immigration to terminate your education extension, you can continue in education as much or as little as you wish. You don't need the education extension to study in Thailand. It is rather, one of the ways (and in my opinion not one of the better ways, if you qualify for other alternatives) in which you may stay in Thailand legally.
I do think you should take seriously the people wondering why you want to switch from a fairly straightforward marriage extension to an education extension with a bunch of weird rules requiring much more contact with immigration and hoop-jumping from you roughly every 3 months, rather than yearly with the marriage extension. Up to you of course, and depends on the nature of your educational pursuits, a language school, versus an actual college or university. The language school extensions are under tremendous scrutiny, at least they were when I switched (which was the reason I switched). A retirement extension (and to a lesser extent a marriage extension) is done and dusted for a year, an education extension (at least one for a language school) is a moving target of shifting requirements and special processing because it is generally not loved by immigration offices.