Mui Ne in Vietnam indeed, plenty of schools there on the beach. Not sure if it will be windy already though!
Cambodia: check out Kampot and contact the guys at Villa Vedici (
www.villavedici.com/) and
www.cambodiakiteboarding.com/ - great and huge flatwater spot in the river mouth, kneedeep water, and no other kiters around. Again not too sure about the wind but when it blows it will be the perfect spot to learn. Villa Vedici is a nice place to stay as well, and if there is no wind I think they can take you wakeboarding to improve your boardskills. Kampot has some other adventures to offer (rent a scooter and drive up the mountain for the view, go to Kep and eat some Kampot pepper crab, do a day trip to Rabbit Island, rent scooters and go find the caves, including the "swimming cave"...).
Stay away from Sihanoukville/Otres beach etc. - unless if you want to hang out on a filthy party beach with dirty old men with barely legal prostitutes, backpackers in their early twenties who look like they're 45 because they've been partying on any drug possible for the last 5 weeks, and annoying hasslers/beggers trying to sell you ****

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