you can visit all the embassy websites and I guarantee you that most of them will state different rules surrounding visa exemption. I mean heck even embassies within the same country have been found to state different things and have vastly different requirements for visa applications.
The only 4 year ED visa you're getting without having issues is from a university. I am 1000% sure you will have major problems at any and all airports in thailand if they see 4 consecutive or even spaced out ED visas from anywhere but a university in the system or in your passport.
regardless of what visa you have, non-b, Non-O, non-OA, non-ED and even the new DTV. If you are in the country for more than 90 consecutive days you need to do a 90 day report.
student visa are under major scrutiny due to abuse of the system, you will likely have problems in the future when entering the country or if/when you apply for a more longterm visa, if you have any type of ED visa in the system that is not from a university.