that is written on the sign at the passport control at least the last 2 3 years : passport boarding pass and visa if applicable. So yes they need and want to see a boarding pass
yes they are very kind in Udon Thani π And fast. When I applied for my 1st 1 year extension of stay they were not happy with some of the photos and my wife's housebook had not been updated with the name change. We were told to just send what they asked for from the Line app π very good instead of having to go back.
not much difference from ETA and the former Thai Pass. The purpose now is to try to keep track of the whereabouts of tourists - pointless in your opinion