I don't recall this being asked before so here goes:

IF you are currently in Thailand on a retirement extension can you simply apply for an extension based on education (with proper paperwork from the school) instead of the usual retirement based paperwork

OR

do you need to travel abroad and start anew with a fresh ED visa?

I'm assuming the latter but just asking.

No I am not really planning on doing this change myself but I can imagine considering it if for some reason there was a problem with a current retirement extension and I could use some Thai classes anyway!

There is no reason in the regulations of police order 777/2551 not to allow as you have the required non immigrant visa entry for any such extension. But do not recall anyone reporting doing this; and in many locations the extensions would only be 90 days rather than one year if just for part time study. As it takes time to get paperwork for education extensions it might not be a viable option as you described above however.

Thanks.

Well if all you could get is 90 days rather than a year for part time study, I reckon it would be well worth it to get a fresh visa out of Thailand.

I believe it depends on what type of study the extension is to be for. If it is for a degree-earning course at a university, immigration will probably allow a change from another type of one-year extension to a one-year extension for studying.