"Within a country, there's also a racial totem pole, with darker people generally closer to the bottom (although there are prominent exceptions, because of religious minorities and similar)." 

I learned that first hand in Thailand about 20 years ago. My gf at that time was from Isan, the eastern provinces of Thailand. It's a very poor region with mostly farms and rice growers. Naturally their skin is darker than the skin of someone like from Bangkok because they're spending more time in the sun. Back then people would judge your richness on the tone of your skin because only poor people have to work in the sun. My gf was using whitening lotion like white people use oil to get a tan. 

It's insane and confirms what you've said, racism among their own kind. Absurd!