Do I personally have to go to the bank and get proof that I have more than 20,000 baht in my account to show the embassy in Vientiane. Or is the paperwork provided by the business I am going to work at showing my salary above thus amount enough?

Thanks Kate.

You need no financial proof to get the single entry non-b visa. See: http://vientiane.thaiembassy.org/upload/pdf/Visa/Non-B business.pdf

I don't think there is any monetary requirements for a Non B. Your employer will provide all needed documents which detail info about the company and its capital. 

You don't need to show 20K to get the visa, however, you could be (unlikely) asked to show 20K in cash/travellers cheques when entering the country.