@Ant **********
doesn't make a difference when it was, if you failed to follow the seasoning requirements you wouldn't get the extension issued,
AND
immigrations could make the case that your extension was void from the date you failed to meet the seasoning requirements.
The only way to solve that problem would be to exit the country get off this current extension and either apply for a new Non-O visa outside the country at a thai consulate or come back in free stamp and apply for the new Non-O visa inside the country at the immigration office
I know people whose balance fell below the required threshold by just a day or two get denied the extension ๐ฎ
Moral of the story FOLLOW the seasoning requirements