I flew BKK-JFK two days ago, booked in premium economy, and got upgraded when I checked in. No idea why - I'm a ROP silver member, will be gold after this flight is credited - but it looked to me like I was already bumped up when the agent pulled up my record.

Not sure if premium was full on the flight. Biz was almost full - I noticed only one empty seat.

It was a very pleasant surprise though.