I arrive in Bangkok on 18 Oct and fly out of there again 18 days later. I had thought of going to Chiang Mai then into Cambodia, but the former seems doubtful now with the weather. I don't mind paying for the visa in order to head to northern Vietnam for a time, but would also like to spend time in Cambodia. I will spend no longer than 2-3 nights in Bangkok then leave Thailand. Is the remaining time (just over two weeks) enough to sample northern Vietnam as well as Cambodia?
Any advice much appreciated!
At the moment there is typhoon and fluting in both Thailand and Cambodia. Northern Vietnam is much better, Hanoi is an amazing city. I when on Hanoi long bay overnight trip, that was fantastic. I booked my accommodation at Hanoi Deluxe Hotel, contact to Ms Moon, she will help you to organize everything.
I think you are smart by staying flexible with your plans. Decide once you are in BKK. I just read an article about flooding in Thailand. Does not make sense to travel up to Ayutthaya or Chiang Mai if they are underwater.
If Northern VN is not having bad weather, then an Air Asia flight: BKK-HAN might be your best option. You can use the visa on arrival system if you fly into VN. My blog covers my experience flying into SGN.
Once in NaNoi, I would then decide what tours were worth your time/money. I chose a 1 day tour of HaLong Bay because of the weather. Does not make much sense IMO for a 2-3 day tour if the water is too cold for swimming or it is raining. Same with SaPa. I would not go there if it is raining. Not much fun slogging around the mud trying to see something IMO.
Send me a PM if you have questions on VN.