There is NO official rule about the length of time a person is required to stay out of the country holding a valid multi-entry visa to thailand of ANY type when they are activating a new entry.
Now if you're talkin' about the southern border crossings with Malaysia, they are a fiefdom of their own. They make up imaginary rules and buffalo people into thinking that's the rule..
Up Bangkok way, the border at Aranyaphrathet - Poipet (Cambodia) is the same way. They're telling people at that crossing they can't "border-bounce" to activate another entry on their visa without staying out of thailand 24 hours.
It has nothing to do with people who are border-bouncing for a visa exempt entry stamp. Especially seeing as the new rule only allows TWO visa exempt entries by any land border in a calendar year.
It is an attempted shakedown plain and simple.