Not sure what a tourist visa will cost you, but a 30-day extension to your visa-exempt entry will cost 1900 baht. It will also require you to prepare the necessary docs for it, the main one being the TM30 for where you are staying. (At least in Bangkok immigration will want one.) If you don't mind that hassle, that should be just fine. But getting an actual tourist visa is not a bad solution. Once in the country, no interaction is needed with officialdom until you are exiting at the airport. Easy in, easy out.