What happens if you don't report to the local immigration office within 3 days of arriving back in Thailand?

The only issue really occurs is when you need to extend or you need something from immigration. No one is checking to see if it being done until you visit immigration. So if you come in on a DTV and leave before your six months and come back and you don’t do the 90 day report, and you have no police involvement no one will no or care.

I rented a house 3 years ago. I've done 2 visas and now on dtv. I bought a new motorbike 2 months ago and when going to get tm30 for transfer immigration still had no check jn for 4 years since 3 old addresses ago lol.

No. Not reporting your stay in China can affect re-entry to China (Beijing specifically) but there is no similar enforcement mechanism for Thailand.

Nothing much to worry about unless you need to do a TM47 90 day report and even then you can just do a TM30 on that day and you'll be fine.

Thailand has a law made in 1979, but it seems difficult to read for lots of people.

The Land owner, OR the house owner OR the landlord OR the possessor of the house reports that a foreigner resided at their property within 24 hours of arrival.

The possessor is the person who PAYS the rent and signed the lease/rental contract.

Just shouting that you as possessor is not responsible is showing you have no clue.

According the same law, the foreigner who is NOT registered is liable for a fine up to 2.000 Thb and the owner of the address up to 10.000 Thb for each foreigner residing.

WHY would you 🚫 NOT follow the rules of Thai Immigration ???

NOTHING ZIP ZILCH NADA Kap

You or the landlord gets a fine. You need the Tm30 for a 90 day report or extension (not that you can do an extension on a dtv).

24 hours. And you get the rack.

The TM.30 must legally be completed by the “housemaster” or relevant authorized person within 24 hours of a foreigners arrival.

The fine for late reporting should not exceed 2000 baht for individuals but is higher for corporate operators.

Not having a TM.30 on file won’t affect you leaving the country but you may need it if you wish to extend within country, file a 90 day report (in some offices) or obtain a certificate of residency for things like a drivers license (in some offices).

You don't do it. The hotel or landlord have to do it. And it's within 24 hours of arrival, not three days.