I heard on today's Thailand base dvlog "20 seconds in Thailand" that new immigration rules just commenced requiring actual return air fare ticket and hotel documents required before entering Thailand. Anybody hear about this?

Nope.

I'm in/out regularly through Swampy and have seen people being asked to show hotel bookings etc but it doesn't seem to be a 100% thing.

So it does happen but as a wild guess it will most likely be asked if the traveller has a few visa exempt entries etc.

gossip