Essentially if you just take your passport and ask for help, they'll be more than happy to do so. I can't stress enough how nice and helpful they were today.
No need for flight or ticket info. You'll need the usual copies of your visa, TM30, passport photo page (or they can do them there for you if you want, think it was 2 baht a copy) and a photo (again, think they can do that there but I took one).
FWIW I got a re-entry permit at the new Central Festival immigration office in Chiang Mai just today and it was a piece of cake. Very friendly staff helped fill out the forms, 1000 baht and done in about 5 minutes. Would recommend!
Doubt it, you're going from a long term visa to another long term visa. The people getting hassle were mostly using tourist visas and covid extensions over and over