Ca$h in Any currency, but MUST be equal to Bt. 20,000....and you must carry it on you when you arrive, there are NO ATM's on the air side of the airports here in Thailand.
Ok, you must complete your 90 day report, between 2 weeks before and up to one week after the deadline date. You must go in person the first time and it is free...thereafter after you are in the system and may file online OR by post.
I suggest visiting a number of schools and observe classes before selecting a program...sit in on some classes and ask questions of the students to get their feedback. When I attended, we had classes for a half-day so some of us could teach for the other half-day as well....and many schools approach TEFL programs to find teachers to fill positions, so it is easier to find work once you "graduate".
, as the others have stated, the TEFL is often preferred by some schools but is NOT a requirement. However, many Academic Directors will give preference to hiring teachers that have completed a standard 120 hrs course, particularly a Thailand based course as it helps acclimate the teacher to better understand Thai culture and teaching Thai students. I did my TEFL in Bangkok when i first arrived, before teaching here for many years. Good luck! You can look at this website to learn more about TEFL programs offered in Thailand and the costs.