Don’t mention anything about employment unless applying for a Non B. Usually people come in on visa exempt and the school will do the paperwork and you’ll usually have to leave the country (usually to one close by) to get the correct visa. You’ll also need to have your documents officiated in your home country. The process changed somewhat recently. I’m not sure how it works specifically anymore.
They’re probably assuming you’re working illegally while living in Thailand on tourist related visas/exemptions. Probably should get a proper legal longer term visa solution. There’s visa agencies in Pattaya that can probably get you squared away for a price.
No such thing. If here on a tourist type visa (visa exempt, voa, etc. don’t mention looking for work, it’s illegal. Don’t give them any reason to not allow you into the country or to think you’ll work illegally on a tourist type visa.
Your fiancé would have the best knowledge on how to obtain that from her local amphur. After she obtains her birth certificate she can have it translated in Bangkok.
Can get translated in Bangkok but you’d have to use the amphur near her village in Roi Et. Not sure if you’ve heard about it but visajourney.com is quite helpful.