yes, same here. I’ve never known Samui immigration want to see a TM30 registration just to extend a visa exempt by 30 days (I’m not saying it’s never happened). Just take your rental agreement and fill out a TM7.
Stamp I mention. Exactly the same scenario as the OP. As Ellie said, just carry two passports. Immigration did the rest with the stamp. This stamp is in my NEW passport. The bit I have scrubbed out has my OLD passport number - linking the two. Done three bounces with both passports and the aforementioned stamp - no problem.
Umm I departed BKK airport, old passport with non imm b multi visa + new passport. Stamp in passport from immigration officer. Old passport number written on it. I speak from experience - not guess.
this is correct. Immigration (when you exit) put a stamp in your new passport and write your old passport number on it. You need to carry both as Ellie says.