What is the process for filing a 90-day report in Thailand, and what are the penalties for late reporting?

A British citizen reported that their DTV visa application was approved shortly after submission in Hanoi. In the comments, discussions arose around the 90-day reporting rule for expats in Thailand, including the process for filing the report, necessary documents, and penalties for late reporting. Key points included that reports can still be submitted without a fine within 7 days of the due date, and fines for late filings are a flat rate of 2000 baht. Leaving the country may complicate tracking of missed reports, and police checks could incur a higher fine if the report is overdue.