A follow up question. If I report truthfully on my immi card at the airport that I am staying at my girlfriends home, do her parents still need to complete a TM30?
TLDR : Answer Summary
The TM30 form is generally needed to report a foreigner’s residence in Thailand, but it may not be strictly enforced unless there's a specific reason to visit the immigration office. While it's advisable to have it filled out, some users suggest that if you're not planning to deal with immigration for extensions or similar reasons, not filing it may not lead to any repercussions. The TM30 needs to be submitted upon arrival but does not require resubmission during your stay unless you move elsewhere.