before you come back and have plan to live here, you should do non-o visa too. Right now they won't open Thai bank account for tourists only long term visa. It might change in the future but from now on you need to check the news from Immigration too.
Depends on what you need to do and what your plan is. Living in Thailand I think income is very important same as other countries in the world. You need to make sure it cover your expenses. For the visa it is not that hard if you got money and prepare documents they want.