Thailand has a large rural population that uses traditional medicinal plants extensively. The country is also the home of many groups of ethnic minorities. But even if much ethnobotanical research has been done in many parts of the country, most studies focused on a single village or a few; only a few of the studies were concerned with comparing the ethnobotanical information among groups or regions of the country. This makes it relevant to compare ethnobotanical knowledge among different ethnic groups in Thailand, including both the rural Thai majority and the various minorities. For our comparison, we collected data about the use of medicinal plants from 64 books, journal articles, scientific reports, and theses published from 1990 to 2014. The data covered 16,789 use reports from 2187 plant species used in 121 villages inhabited by 26 ethnic groups, including rural Thais living in all regions of Thailand. The data were compared using the Informant Consensus Factor (ICF) and clustering analysis. We found that villages inhabited by the same ethnic group often used different plant species while villages in same region had higher similarity of used species for treatments in the same use category, irrespective of which ethnic group that inhabited them. Clustering diagrams showed that similarity in the use of plants was not larger for villages inhabited by the same ethnic groups or from the same regions. So, it appeared that each village had, at least in part, developed its own ethnomedicinal knowledge.