Yes, you get stamped in for a period of 180 days. What has that got to do with 90 day reporting? It says nothing at all about whether you have to do it or not.. I think you are confusing 2 wholly separate things here.
DTV is a tourist visa. I doubt you will get a Thai PayPal account as no Thai ID Card. As for business you cannot have a legal entity in Thailand as above poster pointed out.
You would have to cancel the Non-B then apply for DTV would you not? Leave Thailand without a re-entry permit and your B will be cancelled. Then apply for the DTV?