a) As far as I know, for a foreigner in Thailand a 500K CC limit requires a bank deposit guaranty of 500k. (that's what I have, but for 200k only)
b) I am not sure the transaction would go through, now that the whole system gets paranoid when a white face is involved.
c) I have never said I wanted to transact in cash, I want to be able to draw my accounts down to zero, any time I want, by any means available, without any racial discrimination.