I'm standing by for further clarification from my hotel.

According to the graphic depicting the regulations on the Royal Thai Embassy in Washington website, my situation should be ok. The chart reads:

"Thai nationals and foreign nationals departing from Thailand to eligible countries / territories and back to Thailand are exempted for the 21 day requirement."

That would be my situation. I will have been in Thailand for 5 days in November. Then I, a foreign national, will depart from Thailand in late November, going to only eligible countries, then back to Thailand.

That basically means being in Thailand itself is equivalent to a listed country for purposes of the 21-day rule.

Sure hope that is correct, so I can keep my plans.