Cheers guys. It's answered my question. 2000 baht is less than getting back to bkk now, it seems, so I'm fine with paying that if there are no other consequences. I fully intended to be back in bkk to do it, but then travel got difficult and restrictions extended etc. , so better off staying here!
I was told by my employer and people on this group that you can't change from a tourist visa to a non-b without leaving the country. So best to get relevant documents and enter with the non -b
