@Krystian *****
Your record in the computer will be there tomorrow the same as it was there yesterday.
Nothing resets.
They are looking for trends, and they will use your entire history in evaluating those trends.
It's all about your entry and stay history rather than a specific period of time
*** What seems to be happening is that some people are only being granted a 7 days extension if they have already received a 30 days extension on a previous visa exempt entry earlier in the year.
This may reset in a new calendar year, but if so, it only affects extensions and not the right to enter Thailand on a visa exemption itself.
It depends on your entries and your total time spent in Thailand within a rolling cycle, regardless of the calendar year.