@Dan *******
not necessarily correct and I believe 100% there was a "lost in translation" event that took place.
That's a bangkok stamp and in Bangkok Non-Immigrant visas are issued by counter C-1, <- that's where they applied for 2000baht and that's where they went back to get the Non-B and new 90 day stamp inked in 2 weeks later.
However in Bangkok EXTENSIONS based on employment (as a teacher seeing as they said their school & the school name is written on the stamp in thai) are issued at Counter N-1 <- totally different section
As I said in Bangkok you can apply for an extension when you have 45 days or less <- meaning right up to the last day of that stamp if you want to (although that is not recommended in case you are a document short 😮 )