The objective of this study is to assess the technical efficient frontier of rice farms using input-oriented data envelopment analysis. The frontier represents the minimum applicable level of efficiency of inputs given the current level of yields, technologies, and managerial ability among the farmers which can be used as a benchmark for efficiency improvement of rice farms. Two-stage DEA methodology of efficiency analysis was applied. The empirical results revealed that the technical efficiency of rice farming in southern Thailand could be improved through reduction of inputs by 8-14 % and the current output at 3.5 tons of paddy rice per ha could be maintained. In order to improve technical efficiency of rice farms in southern Thailand, our findings lead us to suggest advisory measures which focus on farm level under existing technology. The optimum rates of inputs for southern Thailand are 123-147 kg of seed, 60-77 kg of N-fertilizer, and 32-35 kg of P-fertilizer per ha. Over the long-run, new rice varieties which suitable for the south are needed. The new rice varieties should be improved from the traditional varieties which included non-photoperiod sensitive qualification.