OP asks: "Why is the medical industry so different? Especially compared to other options such as the Philippines?"
The Philippines are much poorer. And you can get very decent medical care in the Philippines, at prices that are not as inflated as in Thailand (where private medical care is much more expensive than in Western Europe, as read in many posts).
Other South-east Asian countries are mostly much less developed than Thailand (Vietnam, Cambodia, Indonesia) or more developed (Malaysia, Singapore), so not really comparable.
In comparable middle-income countries in South America you are able to find the same levels of care as in Thailand (but even more expensive).
I am not talking about care for the general population.
"Why is the medical industry so different?" Because in medicine, beauty lies in the eye of the beholder. Many patients strongly believe in doctors, procedures and whole medical fields that are useless, if not harmful. To heal a patient, the patient must believe in his doctor. Whereas a car will move whether the driver believes in it or not.
Thailand, the kingdom of make-believe, is uniquely positioned to sell medical services. Many, many patients confuse beautiful exteriors of a hospital with top-notch medicine (another poster mentioned those beautiful nurses in Bangkok Trat Hospital).