you would have to register for healthcare or health insurance in the country you live at present. The NHS cannot treat you while you live abroad I am afraid.
of course they “give a damn” You can’t expect the NHS to give you free or greatly subsidised medication if you reside abroad.(3 months+ is residing abroad )It’s not an international HS.
if you’ve emmigrated to Thailand, you’re not eligible for any NHS treatment, services or free prescriptions. You need to join the health service or pay for insurance in the country you’re living.
It would seem that it’s very straightforward for your Thai girlfriend to get her Thai passport. The problem would be, should you want her to come and visit you in the UK/US ,Australia, et cetera? That would be a completely different ball game.