Can I apply for a Non-B visa to start a small business in Thailand with a 30,000 investment?

You need to legally set up the business before you can get a type B visa. Then in order to work in that business you need a work permit, and that is where the financial requirement comes into play. You must have a minimum of bt2million in registered capital to sponsor one work permit, yours. Also, depending on the business structure you can set up under you might also need at least 4 paid Thai employees for each work permit, but no matter how it is set-up you will need at least bt2million in registered capital for your work permit.