I made that mistake in 2021... I had to pay penalty for overstay and also visa extension..: dumb move ... use the thai passport to come into Thailand and go out (plus thr lines are shorter) then use the USA passport to come back in to USA and also leave USA
Go to any foreign country without a plan where a tourist visa is 30 days and plan on staying for 6 months ... when u get caught you will pay a hefty fine and will get blacklisted and won't be able to come back for many years ...