I will be 50 years old and don't have a good medical record - I'm on coumadin because of blood clots in the past, and had a doctor in New York put on my medical records that I'm an alcoholic. Can I even get health insurance in Thailand considering my poor medical history? If I can, what can I expect the costs to be?

you can get medical insurance easily but the policy will have a clause to exclude any existing conditions. You probably will have to get a medical report too. However

I have never bothered with medical insurance because government hospitals here are very good and very cheap!