@Andreas *******
at least for me, the Chiang Mai office made me get the 30-day extension before I could apply for the Covid “extension,” but the Covid visa was actually considered a new visa that started from the date of issuance, so it wound up overlapping with that 30-day extension instead of getting added to the end.
So, your safe bet might be to get the 30-day extension now, along with all the paperwork for the Covid visa, and then go back to immigration on the 24th with all that paperwork already ready, to see if they’ll let you get the Covid visa. If they extend the program yet again, they probably won’t announce that until the 24th, so you won’t know until you show up.