I will be traveling from Siem Reap to Chiang Mai through Bangkok in November and I am wondering how much time to leave between the flights. We'll be taking Bangkok Air from Siem Reap to Bangkok and Thai Air from Bangkok to Chiang Mai. Is an hour long enough between flights?

it is not any too much....i find that bkk air flights usually arrive early, but sometimes this is not the case...they do load up and move off early sometimes as well...i would not be comfortable with only one hour and you have to do customs as well so this is really not enough time...take the next flight

All the flights we took with Bangkok Air were delayed (or cancelled a couple of times) so I would be cautious. Another alternative is to fly with BKK air to Chiang Mai.

I'd want more than an hour - you have to change terminals from international to domestic

Not enough time. You should change the BKK-Chiang Mai flight to the next flight ( they have about 123 a day so probably an hour later ), no rush, take it easy, change from International to Domestic terminal, go to Thai check-in, check the screens and if by luck you are in time they will put you on the earlier flight if they have time and seats.
Far better than watching the clock all the time.

Not enough time. You should change the BKK-Chiang Mai flight to the next flight ( they have about 123 a day so probably an hour later ), no rush, take it easy, change from International to Domestic terminal, go to Thai check-in, check the screens and if by luck you are in time they will put you on the earlier flight if they have time and seats.
Far better than watching the clock all the time.

I would not make any difference using Bangkok Air to Chiang Mai as you still have to clear Immigration and Customs with your baggage to change terminals, also bangkok Airways have very few flights to Chiang Mai compared with Thai.

Sorry that should be 12 flights ( not 123 ), also sorry for doubling clicking before I finished and duplicating.

Thanks for all of your help! I will make sure to leave more time and push back to the next Thai Airlines flight