The point you’re missing is that there is no such condition as; ‘In theory, once that activity has been completed, the conditions of the issue of the visa have gone, so the visa is no longer valid’.
The question was; ‘what documents have others on a DTV been asked to show when reentering Thailand?’ The answer is none. The reason is because there is no requirement to do so.
Not only the branch. Last week I found I was now unable to transfer more than 49,999 in one day from my Bangkok Bank savings account. We went in and a cashier pointed out that this was my new maximum daily limit. Mrs wasn’t happy, we took another turn ticket and spoke to a different cashier who reinstated my previous higher limits.