I arrived in BKK on a TV on December 1st. I've been getting Covid extensions in Chiang Mai ever since. Up until today, my 60 day extension began from the last visa date in my passport irrespective of when I applied for it. That's now changed and my 60 days are to be counted from today and not from the 18th May which was when my old visa was due to expire.
Just fyi..
TLDR : Answer Summary
The poster discusses a recent change in the Covid extension policy for visas in Chiang Mai, noting that previously, extensions were granted by adding 60 days from the last visa expiry date. However, as of January 25th, the count now starts from the date of application for the extension.