Assuming that you are flying from North America, given the large # of AA miles you have, you could do either Cathay or JAL to Bangkok. Both fly an excellent product via NRT or HKG. It may be easier to book the Bangkok-Vietnam flights with cash as opposed to miles.
There was a promotion that JAL was running on Bangkok Airways flights that was very good for short distance flights (Koh Samui, Chiang Mai, or even Cambodia), but I'm not sure if it's still available.