Chances are you will not be asked. I'd say 99.9% are not, but if you are, it's 20,000 baht in ANY currency. A bank statement will not suffice and there is no access to an ATM
and use either a specialised border bounce/visa run transport agency OR use a Laos border crossing (from reports it appears Nong Khai and Chong Mek are the most user-friendly). Something else to be aware of, from January 1 next year people living in Thailand for more than 180 days per calendar year will become "tax residents" and may well have to produce income/tax paid records for entry above this limit. Thai authorities are well aware that many (and I'm not suggesting you're in this situation) people are working illegally in Thailand whilst staying on tourism-based entries.
I wouldn't be basing my whole travel strategy on one ticket. Either hire an outward bound ticket through onwardticket.com or buy a cheap air or bus ticket out of the country. Some people are saying you can buy a flight to Cambodia for about 800 baht. Don't screw up travel plans for the sake of a pissant amount
If you're going to be in and out a couple of times and spend time outside Thailand (not just a day or two) you'd be better just just leaving and re-entering on visa-exempt basis and getting 30 day stamp each time which can be extended a further 30 days. Keep in mind if re-entering via a land border you can do this only twice in any calendar year
Do you need an excuse not to learn the language? It's not compulsory although it's very useful. I wouldn't be comparing Thailand to the dysfunctional USA
No problem at all. As soon as the money hits your account and is recorded as an international transfer you can do whatever you want with it. I do it all the time. I immediately pay my rent and internet, and within days the electricity bill is paid. 10k immediately goes into my lady's account for the monthly "market shopping" which she excels at. Immigration don't care where it goes, only where it comes from.