That is a good point, thank you.
I'm not sure if I am missunderstaing your post but I do not intend on re-entering with exemption. I plan on re-entering with DTV.
I am on a non-immigrant visa category B and I currently work for a Thai company yes. I have a separate Re-entry stamp that I applied separately for. It is my first year working with this company, so I'm not sure if it is an extension.
The main thing I want to make sure is that I have a valid visa when re-entering. If it's not possible to change this visa on re-entry I guess it's probably safest to leave for a few days, apply for DTV, come back on my non-b visa, if I get DTV approval cancel everything correctly inside Thailand, leave and then re-enter on DTV.