What do I need for TM30 registration while staying at my girlfriend's place in Thailand?

Arriving Thailand next week and this will be the first time I’ve ever attempted, I think TM30 it’s called ? Stayed in hotels before and at my girlfriends place but never seen anything about TM30 until I joined this site.

Not really publicised anywhere for 30 day visa/entry on arrival.

Now my question is while staying at my girlfriends place (don’t think there is a lease)

1. Do I get the signed copy of the Blue Book and ID card or from her landlord ?

2. Has anyone had experience with the immigration office in Ayutthaya ? Can give me some tips ?

I will of course get signed copies of her ID as well.

I have never had to do this before but with the crackdowns etc I’m a little concerned. Last trip the officer at arrival just asked where I was staying and I told him her place he only asked what’s her name. Didn’t appear to write it down just asked smiled and stamped me in.