What are the requirements for 90-day reporting for a retirement visa in Thailand, and can it be done online?

You need to check with your local office for detail.

1) What do I need to bring to immigration (passport, etc) if I report in person?

-> That's otally depending to your local office.

Many offices require you to have your passport, the last 90 days report receipt or notification slip for your first report due date, TM30 receipt, and filled TM47 form, while some offices only requre your passport. The best is to check with your local office.

2) Can I do the reporting online and if so, please send the link?

-> If it's your very first 90 days report, it depends on the local office if they let you do it online. If it's your second or later report, you can do.

Either way, no downside to report online if you are in the window for 90-day report. If rejected, you can go to your local office to do in person.

Online report is here:

90days report windows are:

- At the local immigration office: 15 days before until 7 days after the due date

- Online: from 15 days in advance until the due date