@John ********
I heard the same thing happening at the Golden Triangle border crossing in Chiang Saen. Not a lot of people like to stay overnight in the special economic zone (though the casino is nice) with the cheapest room going for 600 Yuan or 3000 Baht payable in Yuan or Baht and they have Yuan and Baht ATMs in town.
Still, if that's what you're told to do and you use that crossing well, that's what you have to do. Alternatively, you travel to Chiang Khong and re-enter there but I wouldn't push it...by trying to re-enter the same day.