In the corporate world, the Thai philosophy of Sufficiency Economy can be applied to ensure corporate sustainability. This paper adopts Kantabutra et al. (2010)'s ten "Sufficiency Economy" leadership practices to derive measures for corporate sustainability and adopt Avery (2005)'s measures of sustainability performance. A structural model expressing relationships between the two groups of measures is formed accordingly, followed by hypotheses. A convenient sample comprises 112 middle-level managers and business owners who were asked to respond to a questionnaire. Factor and regression analyses are adopted to test the relationships. Findings indicate that (a) perseverance is a direct predictor of firm's capacities to deliver competitive performance, endure crises, and maintain a market leadership; (b) geosocial development and broad stakeholder focus are two direct predictors of firm's capacity to deliver competitive performance; (c) resilience and moderation are two indirect predictors of firm's capacity to deliver competitive performance; (d) geosocial development, broad stakeholder focus, moderation, and resilience are four indirect predictors of firm's capacity to endure crises; and (e) geosocial development, moderation and resilience are three indirect predictors of firm's capacity to maintain a market leadership. Managerial implications are discussed.