FYI:My Extension 30 days was refused at Chiang Mai airport immigration.
I entered nov 2024, extended and did a border bounce (150 days) and went back to Europe
(Also in the years before patterns like that.)
Then I came back 4th of Nov 2025.
First they asked me if I had an outbound ticket (didnt have), then they offered only 7 days which I declined.
I could try at Festival later, but I guess it would give the same result.
Maybe I was just unlucky with an extension on 18 dec 2024 for 3rd of Jan 2025. Maybe it will be granted when I go 19th of dec of 2nd of Jan (last day), but I'm not gonna wait for that...
So, they look probably per 12 months (and not the calenderyear) and they really get stricter...