@Nils **************
I would do it if you're still within the reporting period (15 days before due date, 7 days after due date).
But if you miss the reporting period, absolutely DO NOT pay an agent just to pay the fine. It's likely no one will ever notice you missed the report, and even if they do notice, the fine will be 2,000 baht regardless. You can just pay it then. No need to pay an extra 2,500 baht to pay a 2,000 baht fine.