@Ken **********
During Covid time the borders were closed, so even if an agent could do that (they haven't been allowed to for the past 20 years, with the exception of touts located at some of the Cambodian borders, but I think even they've dried up) there's no way they could have been able to cross the border.
The borders were shuttered and no one was coming in or out. Later on, you could cross but with a lengthy quarantine. Don't think an agent would have been willing to spend 28 days in quarantine (14 days in Thailand and 14 in Cambodia) just to do a border run.
Don't forget that there was the Thailand Pass system in place too, so showing up at the border unannounced was impossible.