I had skin cancer surgically removed at both Bangkok Hospital, Chiang Mai and RAM Hospital. Both were excellent and much, much cheaper than flying back to Australia.
With the income method it is very easy to slip up (or be messed around by banks. 12 monthly deposits sounds sim[le in theory. In pracice not so simple. Exchchange rates can mess it up. Currency transfers can mess it up. Eg, a transfer in 20 Feb (needed as your February payment may, for some reason beyond your control, may not arrive in your Thai bank account until 2 Mar (then no extension is possible). Or one or more transfers may be labled as other than international/ Very easy just to keep 800,000 in a Thai bank - then never a problem.
It is accurate, as long as you have the 800,000 thb in your Thai bank. Over the past 11 or so years I have had extensions based on marriage and on Retirement. Retirement extension is much easier. Wife has to accompany you to Immigration Office for marriage. You need a number of acceptable photos of you and your spouse in various locations at your home. With marriage exension you get a provisional (under considedration) stamp and need to return to Immigration after 14 days to get you full 12 month extension. Immigration may (or may not) require to visit your home and talk with neighbour(s) to confirm that your marriage is valid during the 14 day under consideration period.
I know it is pedantic, but there is no 30 day visa on arrival for Thiland. Depending on your passport you can either get a. a 30 day visa exempt stamp (which you can extend for a further 30 days at Immigration Office for 1,900 thb), or b. purchase a non extentable 15 day visa on arrival. It you intend to visit Thailand, then you need to learn and use the correct (official) terminology.
So, not a real problem unless found on overstay by police or immigration. Then a serious problem - detention, expulsion and ban on reentry. Never choose to overstay.
You should be able to open a bank account yourself, even if you are on a tourist visa or visa exempt stamp. All banks have different requirements. All branches have different requirements. Even within a branch two staff members may give very different answers. Find a branch of the bank you want (I use Bangkok Bank in Doi Saket), in an area with lots of foreigners. Go to the bank with your passport and a friend who holds an account at that branch. Have 100,000 thb to deposit. Should work but many banks/branches will also require a certificate of residence from Immigration. But instead, you could offer a letter from your hotel/ hostel/ Airbnb/ friends house stating that you stay there. Doi Saket Bangkok will work with that.
You should be able to open a bank account yourself, even if you are on a tourist visa or visa exempt stamp. All banks have different requirements. All branches have different requirements. Even within a branch two staff members may give very different answers. Find a branch of the bank you want (I use Bangkok Bank in Doi Saket), in an area with lots of foreigners. Go to the bank with your passport and a friend who holds an account at that branch. Have 100,000 thb to deposit. Should work but many banks/branches will also require a certificate of residence from Immigration. But instead, you could offer a letter from your hotel/ hostel/ Airbnb/ friends house stating that you stay there. Doi Saket Bangkok will work with that