Some of these hospitals have agreements with overseas insurers but I am not sure how that would apply to your individual case.

The membership they sell is targeted at the local market and IMHO great value if you indeed show up for your check-up once a year and do a bit of dental work (Some scaling and free dental x-rays are also included).

One caveat: The in-patient benefits have a 1 month waiting period for new members IIRC. You can't sign up today and claim in-patient discount tomorrow.

Some sales people will not sell Chivawattana to medical tourists, claiming you need to be a resident with proper visa to sign up but as with most things in Thailand there's no consistency and you can get around that by simply going somewhere else to sign up.

I'd recommend you just come here and spend two days to check out the hospitals mentioned in this thread and make your decision then.