I have used it at least twice. One calls the toll free U.S. number and is connected to Bangkok Airways call center in India. There seem to be times when the phone does not get answered, but if one calls in the evening in the U.S. one normally gets one of their knowledgable (I say that in all seriousness) reps. Discovery routings are capacity controlled, they work with you to get an acceptable one.

The pass is costed, you then send a bank check or money order to one of the Bangkok Air offices in the U.S.. They return the paper tickets to you. You do pay for Fedex for the tickets.

Lao Airlines QV does participate in Discovery Air Pass. I assume booking is as above. They also have their own Air Pass (up to 5 segments), but you will find them at a minimum extremely difficult to deal with.

I am planning on writing a Lao Airlines trip report in the near future.