Can I do another visa run to Thailand after December 20th, 2022, or must I wait until the next year?

Understand that there are NO rules about how many border bounces you can do in a year. Also think about the date you did this, December 20th, and why an immigration officer would tell you that with just 11 days left in the year, and your entry stamp being for at least 45 days. How this time frame started being circulated was because a few people were refused entry on their third attempt. If you are actually a tourist, doing tourist things in the country you go to you won't have any problems. If you are trying to stay long term on tourist entry stamps then after the second time you will face serious problems, as you are showing a pattern of trying to stay long term as a tourist, and immigration will refuse you entry. Immigration is very smart, and highly experienced at telling the difference between an actual tourist, doing tourist things, and someone just trying to stay long term pretending to be a tourist.

I would assume that was NOT a visa run. A visa run is traveling to a nearby country to obtain a new visa to return. It was rather a border run / or border bounce. And it would seem to particularly not have involved any visa, but having happened on visa EXEMPT. And thus, visa exemptions are limited to two entries per calendar year (on land borders).

Yes

2 entries per calendar year

You're allowed 2 land entries by visa exempt per calendar year. This resets on January 1st.