Keep going back to the same branch as it depends who you see on the day and what rank they hold. Go to main branches not the malls as the staff at those branches rarely deal with foreigners. I went to same branch of Bangkok bank 4 times before getting an account though I did hold a long term Visa extension. Keep trying or use an agent about 4000 baht.
it most certainly does not but don't give up. Talk to some school directors. A lot of schools have English speaking staff and they might help you. Your chances will also depend on where you are in Thailand. Good luck. All the people I know who have done it say it was a very worthwhile experience.
Visit the schools in your area and ask to see the director. Offer your services for free and see what they say. If they take you up on the offer sort yourself out with the right visa etc. I am always being asked to do some teaching at the local schools but I do not have the right paperwork.