Travelling in Southeast Asia?

I'm looking to go to Vietnam, Cambodia, Thailand, Laos, and possibly India during Chinese New Year's holiday. I will have about 3 weeks to travel. I like history and nature. What places do you recommend I see?

Thailand...

http://en.wikipedia.org/wiki/Thailand

Hope you like it ^^

Thailand = the Grand Palace, Wat Arun, Wut Pho in Bangkok
Vietnam = Hanoi, Halong Bay, Hoi An (very great place), HCM
Laos = There are have a lot of temple there
Cambodia = Angor Wat

All of these country are very great!!!!
I live in Bangkok and love Vietnam...especially Hoi An

All the places that you mention sound great. Three weeks is a good minimum stay.

Love Thailand, the experts say "if you want to see India do it now..In a few years it will be mostly developed like the west and will lose its charm. But 3 weeks does not seem long enough!