At SGN the lounges are operated by an independent carrier; you can pay about $15USD for access.

At DAD you cannot pay-in, and connecting late-night to a following morning international doesn't count.

Arrive early for better seat selection-- forward cabin seats reserved for elites. No online.

Agent in HKG office evidently tried to process an upgrade to business, so they may exist. From what I could catch of the conversation, no one knew how to complete it and she didn't want to call the HAN office again.

No market Sky Priority line at SGN domestic security; I was the only one in it at DAD, and the only person who used SP line at HKG, SGN and DAD.

Service, still relatively disappointing, but Vietnam in what it is.