When do I need to report to police or immigration with a multiple entry non-immigrant O visa in Thailand?

Or when you want the 60 day extension to visit your wife. Then they will be after the TM30.

If you're living in Chiang Mai or Pattaya and staying in a private condo/house you're going to have to report to immigration within 24 hrs every time you enter Thailand to get your TM30 updated. You can skip this if you never plan to go to immigration but, if you ever need something like a Residence Certificate for your driving license or to purchase a vehicle, you will need to go to immigration for it and will be fined. Technically you need to report in all jurisdictions but these are the only ones that seem to be handing out fines.

(y) On that visa you can't stay longer than 90 days per entry so you would NEVER do a 90 day report.

As people pointed out you would required do a TM.30 (alien in residence) form IF you live in an area where the immigration office is hard core about that. However, seeing as you can't stay longer than 90 days per entry before border-bouncing if you didn't need to go to the immigration office for anything, they wouldn't know and therefore wouldn't fine you for not filing one.

How about stating what type of year-long, multi-entry visa you have and where you got it.

90-day reports? If you leave less than 90 days after entry, never.

TM30 report. within 24 hours of arrival if you are not staying at a hotel or rooming house where the landlord has to report you.

Are you referring with this question about the discussion we just had about report to Immigration for notification of stay at a private address?