Silence is golden. Duct tape is silver. Direct deposit in your USA bank. Suck it out via wise or remetly as needed. If they know your our more than 6 months you’ll lose part D for any medicine you need. Don’t announce your plans out loud.
Driving in Thailand is like Mr. Toads Wild Ride at Disneyland. I would fly or hire a car/transport. When we decide to travel we use people that own a van. It holds my wife’s relatives and we’ve ventured everywhere south of Bangkok but going north to chaing mai (sp) we take the night train. The van is comfortable and I think we paid $1200 baht per day.
Medicare will revoke part D if she’s out of the country more than 6 months. However I’ve found my heart meds are cheaper over the counter in Thailand. Check that out.