Do I need to check in with immigration every 90 days or annually on a 5-year multi-entry DTV in Thailand?

Yes. 90 days. If you're in Bangkok do it by mail. Saves that long hike out to CW

Yes

Loaded question

On the initial 90 day report you have to show up in person at immigration

What is initial:

Your initial 90 day report

Anytime you stay >90 or more days from the return of an international trip

if you stay static for 90 days in country the second one you can do online or in person it’s your decision

If you travel internationally every <89 days you never have to do a 90 day report

You can also mail in your 90 day report

Good luck

Every 90 days but only if you stay more than 90 continuous days in the Kingdom (meaning without traveling abroad). So, in the 5-year period you could very well never need to do the report. I'm here since August 2024 and only have needed to do the 90-day report once so far.

90 days

Every time you are in Thailand for 90 consecutive days you must file a TM47, 90-day report. There's nothing to do annually when you're on a DTV.