Buy an elite visa, $17k for 5 years or $30k for 20 years. Otherwise play the game like everyone else and get education visas, volunteer visa, or Non-Bs.
You can't work or obtain a work permit on an Ed visa, only a business or marriage visa (or a ligit volunteering organization). For a business visa you'd need to have a job and be sponsored by a company.
You could apply for it now before you leave. They'll ask you to upload flight details showing your trip from the US to Thailand. I'd recommend booking a flight on Expedia, printing out the confirmation page, they canceling the flight, Expedia has a 24 hour cancelation policy that I've never had an issue with.
Yes it is. For the Evisa flight details you have to say you're leaving from the US, but for actually entering Thailand it doesn't matter where you're coming from.