Via DC-Cam, this paper analyzes Ta Mok's Southwestern Zone under the Democratic Kampuchea regime and the success of the Khmer Rouge "butcher" in crafting a pliant patronage network. It was written by Socheat Nhean for the MA program in Anthropology at Northern Illinois University.

From the abstract:

Patron-client relations created strong socio-political bonds in Democratic Kampuchea (DK). These relations were even stronger and more stable when members of the networks were related, as occurs in the Southwest Zone, where cadres were mostly related to Zone Secretary Chhit Choeun aka Mok either directly or indirectly. Every citizen, both cadres and ordinary people, were aware that life during DK was fragile, and was even more in the later stage of the regime, and this caused people to have stronger ties to powerful persons. In the DK administrative systems, the cadres from each hierarchically administrative unit were closely interrelated and orders were strictly implemented by chain of administrative command in a topdown hierarchical system. Orders were issued from the closest higher echelon and from higher to lower-ranking cadres within each unit. For instance, districts issued orders to sub-districts and within districts orders were issued from secretary to deputy. Orders were followed without fail.

You can read the full-length thesis here on DC-Cam's website.