Yes, needs to be stamped at immigration when leaving Thailand as multiple entry. This is the mistake lots make. This is why I say go to a proper Immigration office like onestop service bottom of Soi 6. There are so many people giving mixed advice that it pays to have someone who's dealing with this every day to make sure its done correctly! Also the Thai visa can and is very complicated!

I think its better just to keep the 800K in your Thai bank account all the time, then it stops all the hassle. I know Onestop Service at the bottom of Soi 6 can do the process for you. His name is Mark and their brilliant. This is what he's text me-

You can use your income method provided. It’s paid directly into a Thai bank account from passive income. You can not use your English. Bank Account is proof to renew the Visa if you wish to use your own ฿800,000 it must be into three months fullfor you to renew it using this method or we can simply take you to the bank and do the funding process for you on the day. Plus bht re-entry permit.

I think it works out about bht total, that's a roundabout about estimate.

Yes you need a Thai bank account and need to show 800,000 bht each year or bht per month for proof of supporting yourself or 400,000 bht per year if you are married. The retirement funds need to be in a Thai bank at least 3 months before you renew your yearly visa. I strongly suggest that you use a agency as you only need to get one thing wrong on the documentation and it will be rejected. I've just completed mine with Onestop Service at the bottom of Soi 6. The guys name is Mark and this service is excellent. Please don't listen to some people who think they know what their talking about, because everybody isn't an expert. I completed my retirement visa, bike and car licence all at the same time. It will cost you but it will save you the heartache of it all going down the pan.