One year retirement visa, register every 90 days. I know you can come in to register anywhere up to one week before registration date, but can you also come in to register up to one week after registration date or have to pay some fines?

The rule as published by Bangkok Immigration is plus or minus 7 days "The notification must be made within 7 days before or after the period of 90 days expires" but I would always try to do a little early rather than late.

One year retirement visa, register every 90 days. I know you can come in to register anywhere up to one week before registration date, but can you also come in to register up to one week after registration date or have to pay some fines?

As an alternative, can always mail it in EMS.  My report date is 2 Dec, I EMSed it on 27 Nov, so should be OK.

Mac

Actually you are probably late as they do not provide a window on mail in reports:

Send the mail before the renewal date 7 days to