Seed is one of the fastest-growing industries in agricultural sector, and maize seed industry in Thailand is one of the most developed and most advanced industries compared to other developing countries. The success of maize seed industry in Thailand is due to public and international organizations’ contributions in building infrastructure for research and promoting the role of the private sector in the industry during the early years, and a long-term commitment of investment in research and development by private companies added to the expansion of the industry. Building on this success, this paper aims at analysing the industry structure, conduct and performance of the maize seed industry in Thailand to provide recommendations for seed business development, and policy recommendations for Thailand to become a leader of seed industry in the region. The results from this study suggest that maize seed industry in Thailand is oligopolistic and moderately concentrated. The business conduct of maize seed firms are differentiation of prices and products, principally varieties suitable to segmented markets. The business performance of the maize seed firms suggested that large multination companies have larger market power from product innovation, but local small business can still profitably participate in the oligopolistic competition environment if they effectively generate sales revenue using public varieties. It is suggested that policies towards building research capacity of local companies will be needed to elevate the competitiveness of local business which will encourage future sustainable development of Thailand’s seed industry.