@Dean *******
you won't get it in writing,
I'd probably try to talk to the section that takes Non-Immigrant Type visa applications at the Chiang Mai main immigration office by the airport
You're far from the first foreigner to wanna get a 90 day non-O using banked money method. I'm sure the question comes up over and over, just go ask. It'll either be yes has to be a foreign transfer or no it doesn't