I'm a retired busdriver myself and only thai native can have a thai busdriver license, I tried myself to get one, car and motorcycle is no problem, but no license for bus. Foreigners are not allowed to work as busdriver, it's a protected job for thai citizens only
all what you need is shown on the website, you can deliver in parts, save it and go further the next day, also it depends on what kind of visa you want. Make sure there is enough money in your bank-account.
E-visa is easy, make an account and fill in the questions, pay online and your E-visa will be delivered by mail, print it and go! It takes mostly just a few days to get the approval.