A great day in Bangkok would be to visit the Jim Thompson House followed by high tea or cocktails at the Oriental.

I echo others who recommend doing at least a 2 day Halong Bay tour - on as nice a boat as you can find. They’re not too expensive.

Angkor Wat is certainly worth seeing but Siem Reap the town is not that interesting. I personally think one full day to tour the ruins is enough.

Hanoi, Bangkok and HCM City are all fascinating and full of things to do. All a bit sensory overload too tho.

Do not go to a water puppet show unless you have super high tolerance for tedium.

I’d cut Chiang Mai and maybe HCMC or trim it down if needed. I’d add more time to Siem Reap. And a little more time to Hanoi and Halong Bay. If I were to add someplace, it would be Luang Prabang.

Okay, I haven't read all the posts. But I have been to these three countries. I think this is way too much go-go-go. With the jet lag, it's just too much.

I'd suggest:
-Hanoi + Halong Bay
-Siem Riep
-Bangkok

Hanoi is amazing. I wouldn't want only a day there. We liked it so much we actually considered moving there.

I really liked Ayutthaya + the cruise. It's a perfect activity with an older adult. I did it in my 20s and still had a great day.

I did an overnight in Halong Bay and it was big fun even though we didn't do much in the water.

I think there's more to see in/around Bangkok than HCMC. There's both big cities. I'd skip HCMC.

I agree with the folks who say Vietnam and Cambodia are better tourist experiences.