Every insurance in Thailand is issued by Thai insurer. They are all equally bad. My Thai wife has 3 insurance policies, one through her employer, one on her own and something similar to life insurance which is actually required and you have to be paying into it for years to actually get covered for anything serious. Oh and of course social security.
Even though she has been paying since she started working at 18 and she is 42 now, she still can not get approved for a simple tonsil surgery. Yearly mammogram check ups or health checkups in general like in every civilized country? Forget about it. Fortunately she gets some of that thorugh her employer.