So, after reading this thread, I decided to go to Khurusapha in person here in Bangkok to try and get some definite answers straight from the source.
There was a very polite man there who was able to answer most of my questions. He confirmed that:
1) If you graduated with a bachelor of education or got your teaching qualification (Masters of Education, PGCE, PGCEi, St Robert Diploma etc) after 2019, you have to do the test to get the 5-year license.
2) If you completed your bachelors of education or teaching qualification (Masters of Education, PGCE, PGCEi, St Robert Diploma etc) before 2019, you can apply for a 5-year license without having to do the test.
3) The only qualification that will get you a 5-year Thai Teaching License without having to take a test, regardless of when you completed it, is a teaching license from your country of origin.
4) Regarding master degrees, a master of arts, even if the area is education, is not accepted/recognized by Khurusapha. It has to be a masters in education (Med). So, an MA TESOL, unfortunately, wouldn't qualify you for a permanent license, which makes no sense, but it is what it is.
5) A Cambridge Delta (Diploma in Teaching English to Speakers of Other Languages), which is a Level 7 qualification in the UK, same level of a master's and PGCE and PGCEi, and which also includes assessed teaching practice, is also not accepted / recognized by Khurusapha. Unbelievable.
Anyway, hope this helps a bit.