I went to Vientienne with all the documents supplied by the school to get a non B visa. Despite having 21 pages of paper, my application was rejected because they said no WP3 document. The school said in 20 years of getting non B's for teachers, they have never asked for this. Is this a new thing, where do I get it from and stamped by who?

Their list of requirements does not mention anything to do with a work permit or an application for one. See: http://vientiane.thaiembassy.org/upload/pdf/Visa/Non-B%20teacher.pdf

Perhaps confusion with a non-b visa for working which requires a work permit application approval letter which sometimes is called a WP3.