When does the 90-day reporting for a retirement OA visa in Thailand start, and how can I report online?

Good luck with CM Immigration - We lived there for a few years and they are the worst I ever seen

A 90 day report is due 89 days from the date you enter the country. They count the day you enter as day one. :O As Richard said you have to do one 90 day report in person to get into the data base and then can use the online program IF the immigration office in your area is participating in it, which Chiang Mai IS (y)

Just so we're clear of the windows of opportunity to do 90 day reporting

In person you can do a 90 day report from 15 days before down until 7 days after your due date

Online you can do a 90 day report from 15 days before down until 7 days BEFORE your due date

Mail in you can do a 90 day report as long as you have it post marked 14 days before your report is due.

90 days is from the date of entry. The first report has to be in person to enter your details in the database. Thereafter, depending on your local office, in some areas and as an option, you are able to report online but only if the web site is up and running. Reporting can be done between 7 and 14 before the due date and 7 days after I believe.