@David *******
SOME Immigration offices (like bangkok) will take your affirmation of income document you present for the Non-O, tell you to go copy it and then stamp and write on the copy that you can use that one for the subsequent yearly extension.
Some offices make you get two documents one for the 90 day Non-O and one for the yearly extension 2 months later.
remember you need a mininum of 15 days left on your current stamp to apply for a 90 day Non-O visa inside the country at the immigration office (except Chiang Mai wants you to have 21 days left) and some smaller offices can't even do the in country conversion.