Is it necessary to print a receipt for the online 90-day reporting in Thailand?

I've previously just taken a photo with my mobile, of my laptop screen showing the "date of next report", and this was acceptable to Immigration when doing my annual extensions.....

Printing it is fine, but I just carry a PDF copy of my phone if they want to see it, but I've never been asked.

If you have to visit immigration that's a different story , I would print it.

Even the smallest village has some sort of print shop

If you don't have a printer just save a PDF until your next visit to a print shop. I understand it's law that you have it attached to your passport

I highly recommend printing out a receipt when doing the 90 day report online, or keeping a PDF copy of it on your computer as proof that you did it. This will give you proof that you've done it in case the 90 day system decides not to work again.

>I have not done an online report

You must have at least one 90 day report done in person, AND you must be in the correct window of time (15 days prior up to the due date). If you don't meet those two requirements, you can't do the 90 day report online.