@Lucien ****
you were not, and who ever told you that was wrong,
the seasoning for the FIRST time you get a year extension from a Non-O 90 day visa is 800K baht banked in a thai bank for 2 months before you apply. Most people provide a 3 month transaction detail report.
For the SECOND year extension you would need to show a yearly transaction report, because you have to show you left the 800K in the bank for 3 months after the previous extension was granted, then the balance never went below 400K baht the rest of the year, until 2 months before your new extension it went back to 800K