Thailand certainly does want long term tourists... but only the ones who have enough money to not worry about getting an elite visa... or the ones who are older.
This is something you need to discuss in depth with your insurance provider and then READ ALL THE DOCUMENTATION THAT COMES WITH YOUR PLAN. You need to make totally sure the details before you sign or pay for anything. Take this seriously, do your own research, and do not believe what people on facebook might say about this.
Facebook is a reasonable place to get advice about where to find good coffee or what bar shows the football game.... but life and death decisions about how your medical insurance works is way beyond the scope of what you should trust to facebook.
don't wait too long before contacting the school to get the ED visa. It can take a month to process everything and if you wait till the last minute you might have to leave the country.