re: Need Advice - Trip to Thailand with a stopover in Dubai

I'd probably do half and half. I don't really see the point of two days in any place jumping to the next, which adding Chang Mai would require, unless it's for a very specific purpose. I had to skip it myself so I could do Bangkok, Siem Reap, and Ko Yao Noi in about a 12 day period. We spent a solid 4/5 days at the beach per my wife's direction, and something like 2.5 in Siem Reap and 3.5 in Bangkok. If up to me I would have added a day to Bangkok and taken one off the beach.

I think an interesting itinerary would be Bangkok for 3/4 days, Kanchanaburi (Bridge over the River Kwai, Erawan Falls) and then Phuket area/beach.

But it's really about your style of travel and if you really need to go balls to the wall then go for it.