The colonial administration was very small, and never numbered more than a few thousand. After independence the number of French living in Cambodia actually increased. When the civil war engulfed the countryside after 1970 it became increasingly difficult to live outside the main cities, and the majority would have left. As you probably know, all foreigners were expelled after the 1975 communist victory. Only one French person I know of stayed through the Pol Pot regime, her name was Laurence Picq and she was married to a communist official. She had a very rough time. http://www.nytimes.com/2007/06/28/style/28iht-aread30-khmer.6380030.html?_r=0