I've never heard of anyone needing a blood transfusion anywhere in Thailand. I've also never heard of anyone having a serious medical problem endangering their life. Suporn does medical tests before surgery to pick up problems. I have heard of one women getting her surgery cancelled due to this.
Suporn's is in a nice modern private hospital. Chettawut has his own small clinic. Personally I find Chettawut's clinic quite off putting, but I don't think anyone has had a real problem because of it.
I'm sure if you had an emergency with Suporn they would take care of you. Worst case it's cheap there. There was a YouTube video recently where one one the parents of a women there for srs had a medical emergency and ended up in hospital. It was handled well. It's in here somewhere
https://youtube.com/user/salaya232/featuredI think it's quite difficult to get travel insurance that will cover medical expenses when you're there for medical tourism. I have heard of someone who had a car accident, I think, and her insurance did cover it.
I don't think it's worth worrying about these kinds of things. They are very unlikely. There's far more likely problems, like difficulty recovery and getting back to work. Suporn's recovery is double that for penile inversion.
From what I've heard of Bank, and the results photos I've seen, he's at least as good as Suporn. Some who have been there are saying he may be better.
Surgeons in other countries have problems too and there's plenty of stories of women being very unhappy about it.