The best thing you can do is to keep mosquitos off of you while you're here. Dengue fever is pretty horrible. There is no vaccine for it either. My husband and I have both had it once. But we've lived here for 8 years now.
The patient wards in Samui hospital (and most govt hospitals) have many patients, are open air, mosquitos in the evening, not clean, and in Samui there were cats and dogs in the hospital as well. I was ok with that part, but the rest was not really ok.
The patient's family or friends sleep on mats on the floor and are expected to stay with the patient at all times.
A private room at the time (2017) only cost 2000 baht per night, so it was worth it.
8 years ago, we sold everything left the US with nothing but 2 backpacks. Been here ever since. Our only regret? Not having done it sooner!
If you're not 50 or over, a long term visa will be a challenge. If you're 50 and up, you can apply for a retirement visa. You'll need 800,000 baht each in a Thai bank account, I believe insurance, and lots of paperwork! Best advice is to visit a Thai embassy in Canada and speak to them about options. Good luck!
I had major (non life threatening) surgery on Koh Samui. Before we left the US, I had been quoted $35,000 for just the surgery (not anesthesia, room, etc). Insurance wouldn't cover, so I had it done here in Thailand.
I found a good recommended surgeon first, and he gave me an option to have it done at an international hospital (200k baht) or govt hospital (100k baht/$2857 usd).
I chose the govt hospital with a private room instead of patient ward, and it was great!
This price included everything. All in! No extras of follow up.