In general, there are just two types of English language teachers in Thailand... Professionally qualified teachers with a teaching license from their home countries (of either America or the UK) who will accept nothing less than a well-paid job at a properly accredited and respected international school... and then there's everybody else.
All the 'qualifications' (TEFL, CELTA, etc) for those of us in the 'everybody else' section are NO MATCH for the opportunists among us who look for great jobs and make themselves available when they appear.
Thai employers simply don't care about your bits of paper - except for the one that says you have a bona fide degree. Most of them wouldn't even know what they are or the differences between them. Even if they did, they wouldn't care and you wouldn't be paid more because you have them.
Doing these courses may prepare you to be better equipped to deal with a classroom of Thai kids... they will do NOTHING to impress a Thai employer or make you better paid.