Khao Sangyod (Sangyod rice) is an indigenous red rice variety commonly cultivated in Southern Thailand. Its distinctive and desirable cooking quality and nutritional value made Sangyod rice in Phatthalung province Khao Sangyod Muang Phatthalung the first geographical indication (GI) rice registered in Thailand. These attributes also earned it the status of a Protected Geographical Indication (PGI) Thai rice registered in the EU. Sangyod rice cultivation can generate a good income for farmers and contribute to the conservation of indigenous varieties and genetic biodiversity. This study aims to measure farmers’ net incomes (profitability), which is one important indicator of sustainable rice platform (SRP) indicators by the United Nations Environmental Programme, and to compare the profit inefficiency among farmers. The data were collected from 328 farmers in three southern provinces for the 2019/2020 cropping season. The results show that, on average, Sangyod rice farmers have a profit efficiency score of 68, implying that they can still improve their profit by 32%. Sangyod rice production in the GI area has a profit efficiency higher than that outside the area. The results from this study can inform the formulation of policies that support the sustainability of indigenous rice in Thailand.