Its not a border bounce for visa holders with multiple entry. That is a term used for people on visa exempts abusing the privledge, I would make sure you have proof of the 400k baht in savings they are asking to see that at immigration with the DTV and other paper work its random but id be ready to show your documents
Yes for DTV yes its required, if you are from any 35 plus nations you can visit thailand for 60 days free on visa exempt 1100 baht extension for 30 more days