Now
@Ga**
, you don't need to speak thai OR pay someone to push-paper to apply for a Non-O inside the country :/
Most immigration offices have a sheet in both thai & "engrish" that states exactly what you need to do a conversion from a 30 day visa exempt stamp or a 60 day tourist visa stamp to a 90 day Non-O.
Be advised, IF you're applying for the Non-O in bangkok based on being over 50 using 800K baht banked it IS a requirement that you show the money was transferred in from abroad.
You need to have a print out from your originating bank showing the swift code transfer to your thai account.
The good news is there is NO seasoning requirement when apply for the initial in-country Non-O.
That's only when you apply for the yearly extension. You could have transferred in the money yesterday and applied today as long as you can show it came from outside the country into your thai bank account.