English is the world's global language. All Thai embassies and consulates worldwide accept and prefer English or Thai language documents where possible. In most locations, it's required. A few European ones might also accept documents in the language of the application country too, such as German or French.
What country in Africa are you headed to? It sounds like you're coming to America first before traveling out to Thailand. Therefore, if you're going to a yellow fever country, unless it's a requirement for entry to that country you won't have to worry about yellow fever vaccination.
The USA doesn't require it, regardless of where you're coming from and since you'd be traveling to Thailand from the USA, Thailand won't know you've been to a yellow fever country...that is, unless they were to spot a stamp from a yellow fever country in your passport. Having said that as long as more than 10 days have elapsed since leaving a yellow fever country you're good for Thailand as well.
I wouldn't have attached your AMEX statement. Also, Amex isn't widely accepted in Thailand. This is VISA/MasterCard territory and the 3rd most accepted card is UnionPay. 4th is JCB. Amex comes in at a distant 5th.
Anonymous participant 812 You definitely can't. Now with bank accounts being closed for tourist visa holders, your "credit card" will also be, in the unlikely event the bank was stupid enough to give a tourist a "credit card".
In the past, a lot. These days, I'm not sure. It's not a good option for long-term stay. Fine if you're a genuine student to get through the first 6-12 months in the country.
True, but I think as long as you're actually attending such courses, all is well. I can totally see Thailand NOT granting visas for such courses, for longer than around a year.