Thailand’s rice has set a supreme quality standard in the world market. Seed is one of the important factors contributing to good quality grains. As the competition for quality rice in the world market is becoming intensive, rice seeds play a significant role not only to ensure food and income security but also to retain quality and competitiveness of Thai rice in the world market. This paper reviews policies and regulations related to rice seed industry in Thailand, current situations of rice seed system, the supply and demand of rice seeds, and implications for future rice seed industry development. It is found that some of current regulations and business environment do not create much incentive for investments for the private sector. The imports and exports of rice seeds are practically prohibited. Thus, most of existing rice seeds in the market comprise of mainly public varieties produced by formal seed sector with a few exceptions of privately developed varieties by Thai companies, farmers’ groups and research institutes. None of the foreign stakeholders is in rice seed industry in Thailand presently. As seed producers do not hold exclusive rights to reproduce public varieties, and because all of the varieties are not hybrids, informal seed system is the major source of rice seeds. The systems of rice seed suggest that formal and informal systems can be integrated and linkages between both systems should create incentives for business opportunities.