Yes they check it. I had to do it at Suvarnabhumi a couple of days ago, at 1 am. My phone died but luckily they have some machines to do it and it doesn't take much time at all to fill the form. The immigration officer knows whether you've done it when they check your passport in their system.
It worked for me two weeks ago. Now none of my cards work, payment gets rejected every single time. I use two different cards from two different regions, none of them work. I can use them on bolt and grab though.
applying for DTV is a lot easier than doing your tax though. If you're not even able to fill a form and provide a couple of documents it's to wonder how you can be a functioning adult
I'll also add that there isn't any clarification coming from the authorities about this. It all comes from third party websites, and as I said there doesn't seem to be a clear consensus. Not saying you're wrong, you probably are, but it's no wonder people would get confused when even the experts don't necessarily agree on this.
on experts who say it counts as "remittance" and those who say it doesn't. I even saw a guy that said he asked at a tax office in Bangkok and they told him it doesn't count. Anyway as you said it's hard to enforce because there's no way for the authorities to verify what is and isn't foreign revenue. And you would most likely be covered by an agreement between Thailand and your home country anyway.