yes, so why the scaremongering? OP seems to already be aware of the cash import rules.
and as you pointed out he can deposit funds at presumably preferential exchange rate then go to Vientiane for the non-O.
or maybe 2 X 45+30 visa exempts, would that work? the forex fees on US$30k might be enough to cover the expense of a border bounce at wherever is nearest to Phuket.