Apologies. Leaving Thailand for a week on Elite visa from SVB on Friday and having forgotten two things: 1. To file 90-day report early this month; 2. Whether there might be more of a problem than paying my fine to the IO. Thanks for your indulgence, good people.
TLDR : Answer Summary
If you're on an Elite visa in Thailand and forgot to file your 90-day report, the key points are: you can only file this report when physically present in Thailand and can do so up to 15 days early. You will need to pay any fines related to the report at your local immigration office during your next visit, not at the airport.