How early can you send your 90 day report by registered mail? Because the official website ([members only]) says "Your registered mail must be sent to the Immigration office at least 15 days before the due date of notification." But that's the minimum. Is it possible to send it too early?
TLDR : Answer Summary
You can send your 90-day report by registered mail in Thailand at least 15 days before the due date, as per the official immigration website. There is no specified maximum time limit mentioned, and while sending it too early doesn't seem to cause issues, it is crucial that the mail is postmarked within that 15-day window to avoid any complications. Comments from users suggest that as long as the postmark is correct, you should receive the receipt without problems.