Edit: Looks like my below speculation is wrong.

Literally the least knowledgable about this but I imagine you just go to a random clinic/hospital offering walk-ins and ask for one. Google says they're "quite cheap" (<1500 baht?).

@Darren ******

So it doesn't matter that I'm stopping in BKK first?

@Darren ******

But Chiang Mai has approved blue zones within, like, thirty minutes of CNX.

@Michael *******

That's for sure 😅 Thanks a lot for responding to me again, you've been very helpful

@Michael *******

Thanks for responding. I think I will ask for a stopover in BKK so that I can do the one day quarantine, and then continue on to Chiang Mai.

Sorry, could you expand on this comment? I was able to book a flight to Chiang Mai last week; the flight stops in BKK and then goes to Chiang Mai via Thai Airways. Now I'm questioning if I need to do a stopover in Bangkok to do the 1 Day Quarantine, or if I'll be able to do that in Chiang Mai (because on the AQ directory website, they do have a Chiang Mai AQ hotel pending...)

At least on American passports, the stamping area starts on page 8.