usually most of the Banks dont entertain if you are on tourist visa or visa exemption. They may ask for the letter from your embassy. I had shared information to your inbox. please read that. Hope that may help you
Please counter check from different sources as well. I had shared some more information in your inbox. Hope those info will help and suit your requirements
Yes you should do like that first. Since you are SA national, you can get 60 days visa exemption with 30 days extension. So, you can stay 90 days. Do like this for 2 to 3 times and then visit various places in Thailand before taking final decision. Tastes and preferences of all of us are not same. May be the places I like you may not like. If you need any further information, feel free to ask
Before doing so, I would recommend you to come and live in Thailand for few years at different places. After few years you can then decide where in Thailand to settle forever. Do your good homework before take such huge decision. But overall, thailand is really very nice place to retire.
If you are 50+ years old you can go for retirement visa with multiple re entry permit. With this multiple re entry permit, you can go in and out of thailand any number of time