I cross that border 4-5 times a year. Never a problem. It’s people doing border runs and living in Bangkok (as it’s the closest border to that that city) on visa exemptions who encounter problems.
they get it from all the embassies of countries where the chances of "pulling a fast one" are high. We're aware of that. I know sooo many illegal workers back home it's insane. Stop butthurting, that's just the reality of the world.
you have 2 options: the banked 400k or proof of monthly income coming from outside Thailand. I think that number is 45k... Better check with any Thai embassy website, the numbers are the same for everyone.