I though, If you are in hospital whilst your visa runs out (you will be overstaying before you can get to immigration for an extension of stay) but with the doctors certificate you go to immigration to get a (backdated) extention of stay. You will not be fined Overstay.
I hate standing behind 400 noisy Chinese tourists arriving in Surat Thani every time I come back from KL. Until now I used Paracetamol but Express Service sounds a lot better. Wonder if they offer that down here?