'Visa end" and "end of the permission of stay" are two different things.
Visa expiry date means that is the last day to can enter Thailand with that Visa and you get a permission of stay according to your visa type when you enter.
When you enter Thailand you get an entry stamp with the date of the last day of your permission of stay.
You don't get x-ray, cat scans or an emergency crew if you have dengue. Maybe two, three days hospital, 1'800THB. Blood test 1'200THB, some saline solution and antibiotics and the attention of some pretty nurses during your stay.
A single CAT scan can cost anything between 5'000THB to 40'000THB. Chest X-ray 1'200THB
How long you stay doesn't really matter as 400THB resp. 600THB for bed and food is the smallest cost.
Anyway, why would they rip me off? My Thai insurance paid for it and I'm sure, they don't allow themselves to be ripped off.
How can you assume how much hospital admission costs without knowing what was involved?
Just got out of hospital today after having an emergency admission for acute bronchitis and two nights in government hospital in the general ward. 24'800THB
60 day Tourist Visa is cheaper (around 1'000THB depending on the exchange rate) and less hassle to get then entering Thailand on Visa Exempt, then travel and hang around the immigration office to extend your visa exempt for 30 days for 1'900THB