The type of agrarian structure employed to produce tropical commodities affects many dimensions of land use, such as ownership inequality, overlapping land rights and conflicts, and land use changes. I conduct a literature review of historical changes in agrarian structures of commodities grown on the upland frontier of mainland Southeast and South Asia, using a case study approach, of tea, rubber, oil palm and cassava. Although the production of all these commodities was initiated in the colonial period on large plantations, over the course of the 20th century, most transited to smallholder systems. Two groups of factors are posited to explain this evolution. First, economic fundamentals related to processing methods and pioneering costs and risks sometimes favored large-scale plantations. Second, policy biases and development paradigms often strongly favored plantations and discriminated against smallholders in the colonial states, especially provision of cheap land and labor. However, beginning after World War I and accelerating after independence, the factors that propped up plantations changed so that by the end of the 20th century, smallholders overwhelmingly dominated perennial crop exports, except possibly oil palm. Surprisingly, in the 21st century there has been a resurgence of investments in plantation agriculture in the frontier countries of Cambodia, Laos and Myanmar, driven by very similar factors to a century ago, especially access to cheap land combined with high commodity prices. As in the last century, this may be a temporary aberration from the long-run trend toward smallholders, but much depends on local political economy.