if you are not legally registered for marriage I dont think you will have anything in the way of inheritance, the same with your Visa. You could obtain a retirement visa if you are over 50 and have the necessary bank balance.
I had a bad infection in my foot following an insect bite. I went to a Bangkok hospital in Ratchaburi and was met by a manager (not a medical person) who informed me that I would need an operation and would be in hospital for at least 4 days. She was interested in only my ability to pay. This continued throughout my stay. It disgusted me and in only confirmed my belief in a national health service.