Another good reason to get a pink card. The seniors' cards on both MRT & BTS do not expire. BTS had a big crackdown, or at least the announcement about fining riders B2,000 for improper use of student or seniors' cards.
I've had absolutely no problem renting in Canada with my Thai licence. I do try, however, to use a CAD credit card to provide full insurance.
My guess in the U.S. that they can't fathom a Thai licence is for real!