Appointment slip and invitation letter are eligible to apply soft power medical treatment which must indicate to need long treatment such as diabetes, cardiovascular and hypertension etc.
Since I have applied in Consulate Malaysia, I only provided hotel booking from agoda. It is not essential, I think. I was asked by Visa officer that why I need DTV instead of non immigrant O visa (Medical Treatment)?
What treatment are you required short term or long term? Some treatments need a short term may be a few months which is questionable for DTV medical treatment. Some are going to long term treatments which is reasonable for eligibility.
My knowledge and experience, long treatments of Diabetes, cardiovascular and hypertension which all need lifetime treatment. I have explained well in Malaysia.
Some hospitals are able to provide appointment slip and visa invitation letter with attendant. If chronic disease such as diabetes, hypertension, cardiovascular disease are considered long term treatments.
It is more convenient than other soft power Muay Thai and Culinary class.