Over the past few decades, increasingly intensive maize farming by smallholders in the uplands of northern Thailand has produced a maize boom that has fed the country's livestock industry. Despite continuously high demand for feed maize, its cultivation has declined unexpectedly over the past decade, pointing to a major land use transition in the uplands. This study investigates the causes of this maize bust and its accompanying land use changes from the perspectives of smallholders. Drawing from fieldwork in the northern province of Nan, we examined their household-level decision-making, challenges, and future visions around land use and livelihoods. Data was collected through a survey of 347 households across 10 villages and semi-structured interviews with 45 smallholders and 8 of their children. We found that many smallholders are being squeezed out of maize because of surging production costs and labor shortages due to aging and the economic out-migration of younger household members. However, rather than abandoning farming altogether, these smallholders are investing in less labor-intensive perennial crops for livelihood security amidst an uncertain future, signaling a pivotal land use transition in the northern uplands. Our data suggests that the ability to make this transition depends on access to land and financial resources. This raises questions around policy support for smallholders with fewer resources who remain dependent on maize despite the growing production risks.