I work in a government school in Issan which employs several teachers that do not possess degrees or fake degree certificates. They have work permits, one has been teaching at the school legally for several years and one has recently received their work permit and teaching license. I do not have a degree but the school still offered me employment and a non-imm B visa and are currently in the process of applying for my teachers license. Like many things in Thailand, it is often not a case of what you know but who you know, if the school have connections at the MOE and you are happy to live in the North East where the level of English is extremely low and there is a huge shortage of teachers it is possible to teach legally without a degree. I also know several other schools in this area that are legally employing teachers without degree certificates.
The salary I receive is low in comparison to what many private language institutes or international schools offer, but it is still three times what many Thai teachers are earning in the same school, and I can afford to have a good quality of life here (the cost of living in Issan is also very low). I also have friends legally teaching in Chiang Mai without degrees or fake degrees but I believe it was harder for them to find employment