Go to the office at Prom with passport and TM 30 receipt “update no changes”. (Obviously you can’t report within 24h if immigration is closed and I have “heard”there is a 7 day grace period for updates). I have done it many times if there is short queue of people very quick process.
In the same Chiang Mai Condo for 8 years suddenly having to pay a 1600 baht fine for not filing a form that was never before requested (TM30) was not the fairest, they could have had a notice/anmesty period but my arttitude is OK No Problem Khrap. Now almost every time I go in there now there is some old coot making a fuss.