You seem to be referring to the ETA requirement that may happen on Dec 1st. There have been press reports of this, but like many instances press reports aren’t law and are quite often way off base. We will have to wait until there is anything officially announced.
It can happen. It’s one of the “requirements” to enter Thailand. Except that it’s almost never asked for. I suspect that for whatever reason you may have riled the officer up the wrong way. Just a guesstimate on my part but usually they’d never ask for that.
ok that would be incredibly unusual. But as anything immigration wise it’s up to the individual officer you hand your passport to. If they are having a bad hair day then they can ask for stuff that 99.9% of other people would never be asked for.
Immigration almost certainly won’t ask you for onward flight information unless they are looking for a way to deny you entry. Obviously that rarely happens to anyone who is a “normal” tourist.
If you’ve got a history of previous entries on tourist visas or visa exempt entries then they could ask. They believe you are abusing the system.