they want 800k for the first year because they don’t know your income. The second year you can prove the 65K baht per month with records and then the 800k isn’t required.
My advice is to apply online from your own country. Secure the Visa before arrival. As far as working in Thailand it might be somewhat difficult to get a work permit. Maybe consider hiring an agency that can guide you. Good luck.
I used EVA Air and it’s less expensive to just buy a round trip ticket. You go thru Taipei to Bangkok. Get online in the USA and do the visa because 30 days isn’t enough time. Good luck