you can use a visa debit card to pay AUD. As for documents you need passport photos taken. I would do it first at the recommended shop in Sathorn. The embassy site has info
I have used single entry tourist visa, ME spose visa, Spouse extension and re-entry, and multiple 30 day exempt. I dress well an am polite. I never have a problem at BKK. DMK always question me, visa or not.