- if your arriving on visa exempt (and then 30 day extn) you probably have enough time to convert to non-0 - assuming you get to immigration and all the paperwork in order - the application goes under consideration for a few weeks (sorry I forgot how long exactly)
A single entry tourist visa is valid for entry into thailand for 90 days, on entering Thailand you'll be stamped in for 60days (which can be extended by 30 days)