This paper attempts to explain why Karen do not cultivate opium poppy in a region where offers highest cash returns for any crop. Its initial claim is that their small nuclear family production units simply lack manpower for intensive cultivation which poppy requires. But this argument raises further questions. Is Karen social system so inflexible that its members are unable to bend rules to suit their circumstances? Are there any aspects of their system which allows them scope to maneuver? If so, to what extent are these utilized? Or, if their system serves them so poorly, why does persist? These questions lead to highly controversial issues which cultural ecologists and evolutionists have debated among themselves and with their critics about nature of human adaptiveness, character of social and ecological systems, rationality of social systems, and forces which promote social change. It is obviously beyond scope of a short paper to tackle these questions head on: nevertheless, I can illustrate how insights can be gleaned by focusing on what Vayda (1967:10) has called the areas of disorder?the parts of social systems which outsider perceives to be out of tune with socioecological structure as a whole?rather than on parts which appear to be in harmony with one another. By so doing one might better isolate points of stress in a system?the points at which fission of one sort or another is most likely to occur?and thus improve understanding of dynamic processes. The economic advantages of poppy cultivation are considerable, despite a widespread impression to contrary. Opium poppy is only one of many crops grown in large hill area extending over provinces of northern Thailand. Rice, grown in swiddens or irrigated terraces, supports most of inhabitants at a subsistence level. Cash crops other than opium include sesame, tea, and vegetables but are of little importance. Lowland based commercial enterprises include tin mining and forestry but are not highly developed. Those who cultivate poppy are by far most prosperous farmers in hills. No doubt poppy cultivators are poor by Western standards, and their returns per unit weight are miniscule compared with those who traffic in heroin on streets of New York or Sydney, but by Thai standards they are rich. Geddes (1967:197), after an extensive comparison ofthe available data, concluded: it is clear, therefore, that in good years average Meto (Hmong) family could achieve an income through opium production several times higher than that