Cathay still officially serves CMB from Asia, no? It doesn't seem too far-fetched to assume that (someone) will issue a ticket with HKG-CMB open, and Cathay will generously drop the pax on their heads in Bangkok as they're doing with existing tickets.

It would seem that the big deal will be getting someone to ticket eastbound out of CMB. I'd hate to be among the first hundred people to approach RJ with the thought of an xONEx in mind. But AA seems super-friendly about allowing its far-flung GSAs to use its stock for such things, so maybe the AA GSA in CMB would be a good place to start.