@Seaton ************
and they're preparing for you the needed documents to obtain the Non B visa?.... OR as you are now an extension of stay as a teacher...with the cooperation of your new employer and Thai immigration office in Surat Thani and your current Thai immigration office... explore getting the reason for the extension of stay to be your teaching in Surat Thani.
Let's await the morning in Thailand as it's late night now...
I have asked our Moderating team to review your post and reply with their suggestions about your options.
Monday is already August 1st.. AND you have an employer to start teaching Thursday August 4th...
I am NOT certain that you have the time needed to do this. It's a huge challenge.