Some do not know what a 90 day report is and other recommend to use TM47 and TM30, and you can do it Anytime.
It seems lots of you are not even interested in following Thai rules and regulations.
But okay.
You need to report to the local Immigration Office if you are staying 90 days consecutive inside Thailand. The day of arrival is day 1.
You make the first report in person, you bring your notification of stay, the paper you got from your landlord/house owner after your arrival at that address.
And you bring your passport, most immigration offices can scan your passport and will print out with all the date filled in, a form which you have to sign.
You get a small piece of that form with a NEW date to make your next report.
You visit the Immigration Office where your address is registered between 15 days before due date until 7 days after.