I have no feedback or experience with Thailand liveaboards but 10-12 days for land in Thailand and Vietnam doesn’t sound like enough. Could you do just one or the other? (Thailand was fantastic!) Then again, I could easily burn many days at the beaches.
I could be wrong, but I interpreted
@Scubagolf to be saying that they plan on 10-12 days of topside travel in Vietnam and Thailand (I assume Vietnam first) and then an
additional week on a liveaboard in Thailand. If I am correct, I am just going to comment on the Vietnam portion at this point and will need some additional info and confirmation B4 commenting on other ideas.
Topside in Vietnam, depending on # of days, I would prioritize the following:
1. Hanoi is an amazing city. I just love it for so many reasons.
2. Halong Bay is a must see and must do. Give yourself 2 days and 1 night on a houseboat. Plenty of tour companies in Hanoi offering this trip with daily departures from various downtown Hanoi locations.
3. Since you posted on Scubaboard and are a diver, then I'd make my way south from Hanoi along the coast via train/bus and give myself a few days in the gorgeous and historic Portuguese/Vietnamese port town of Hoi An. I would also, at a bare minimum, give myself a 2 tank boat dive excursion from Hoi An out to the Cham Islands. Great day of diving and buffet lunch on one of the island beaches.
Cham Island Diving – Hoi An, Vietnam or
Hoi An Diving Center, Five Star PADI Scuba Dive Center - Hoi An Diving Center, Five Star PADI Scuba Dive Center
4. I would go nowhere near Saigon and then just hop over to Thailand for the remainder of your topside days prior to a liveaboard.
5. If I were to do a liveaboard out of Thailand, then I am heading up to the Similans or Mergui Archipelago (Burma/Myanmar) for sure.
6. Your timing is perfect in terms of time of year to dive and visit these 2 great countries. Dry season and cooler topside temps.