a few things here
Cambodians and Laotian people are not the same..so not sure hwy you are lumping them together..
do you live in California ?
as far as the skin tone goes, thats about the norm for cambodians

Laotians get dark as well and some Vietnamese and filipinos can get dark as well
here in the bay area every city is pretty much 5-25% asian and each city seems to have a majority asian for the most part, as weird as that is..
San Francisco - Chinese
Daly City - Filipino
San Jose, Vallejo, Fairfield - Filipino
Richmond - Thai or Thai/Mein
Oakland - Cambodians, Vietnamese and Laos
and while you can find them scattered through out the bay, its crazy how they have super concentrated overly majority of those specific in those areas
then you head up to Sac and start seeing Hmong and more cambodians, laos and thai
edit: theirs almost more asians than white people in the bay area now