Sometimes it’s not just for security, but they don’t want you logging in from overseas, because if you are out of your own country, they don’t want you to have the account or have additional restrictions.
you get the visa once and extend each year, but you have to maintain money in thai bank. My concern is they’ll raise required banked money, not the small fees to get or extend visa.
in the past they grandfathered existing visa holders to the previous amount in the bank. This is the current ฿800,000 in bank, not the ฿1900/year to extend the visa.
I do plan to keep my retirement visa if I leave, because if I want to move back, they may raise the amount you have to have on deposit to an amount I can’t afford. 
if you can get a tax ID and give the number to them, they will stop deducting the tax. I think the tax is 15%, and it’s possible to file a tax return each year and get the money back, but the process is very cumbersome.