What Are the Rules for the 90-Day Report in Thailand?

You need to report your presence in Thailand if you have been physically staying in the country for 90 days. There are different methods to file this report: you can do it 15 days before the 90-day mark by mail to the Immigration Office, between 15 and 7 days before using the Online System (if your registered data remains unchanged), or in person or via an authorized person from 15 days before to 7 days after the 90-day due date.