I self insure because I have to. 80 yo, pre-existing conditions. An application from me here would probably cause merriment among insurance writers..
I do, however, have top level private health cover in Australia. If I have a heart attack or stroke, so be it. Anything else requiring hospital, I am on a plane to Australia.
I checked health insurance premiums here when I was 72. IIRC it was 300,000 baht/year with no pre-existing conditions.