The paper discusses forest habitat classification system used by the Pwo Karen in Thung Yai Naresuan Wildlife Sanctuary in western Thailand and the Non-Timber Forest Products (NTFPs) gathered in these habitats. The paper argues that the Pwo Karen have two methods of forest classification, and that these are closely related to their swidden farming practices. The first is used to classify forestland that has been, or can be, swiddened, and uses the age of the vegetation to essentially indicate if the forestland has been left fallow for sufficiently long and is now ready for farming again, or if it has been left fallow for too long, and the effort involved in clearing and burning the forest is now too high. The second system is used for land that is not suitable for cultivation, and looks at soil properties and slope. The paper then turns to the wild vegetables that the Karen gather from the various habitats, and which together account for some 80 to 90 percent of the vegetables they eat. The article describes the quantity of wild vegetables that the Karen gather during the year from each habitat, including the seasonal variation, and provides an estimate of the economic value of these wild vegetables, using comparable vegetables sold in the market as a proxy. The paper concludes that the amount of NTFPs available in each habitat has influenced the forestland management of the Karen, notably their choice to set their villages near the river, and not to cut the forest near their villages. Knowledge of the habitat of origin of NTFPs can have important implications for policy planning, especially when the government interferes in swiddening practices, thereby altering forest habitats.