I am about to switch my Star Alliance program from TAP to either Asiana or Thai Airways since I recently lost status with TAP. The reason I am keen on Asiana or Thai is the qualification period is 2 years rather than Gold which makes it a no brainer. It would be a second no brainer to go with Asiana over Thai (lower Gold qualification requirement) if it wasn't for the potential takeover by Korean Air (which may or may not succeed). My next Star Alliance flight is this Saturday with Air China. I will register for both Asiana and Thai Airways programs on Friday.

My question is: If I don't record my program number (neither Asiana or Thai) on the boarding pass, can I still claim under either Asiana's or Thai Airways' programs after the fact? The timeline for both for claiming missing miles is clear (Asiana is 1 year, Thai is 180 days, but what if my boarding pass doesn't show the program nunber?

In short, I am looking to keep my options open for a long as possible as to which program I credit my upcoming flights to. If it becomes clear that the Korean Air takeover of Asiana will go ahead, I'll go with Thai. Otherwise, I'll go with Asiana.