Due to the diversity of Thai cultures, dialects, and environments that vary according to the regions, causing questions about the color names in Thai. 330 Munsell color chips were employed to obtain the color names used by 100 subjects(25 people per each region)using categorical method with monolexemic term. There was a similar mean number of color term usage in each region. Considering the consistency of the color name used by ≥80% of subjects found 12 color names, these included 11 basic color terms of Berlin and Key(1969)plus "Fa"(Sky)that was used by 100% of subjects for all region. There for, “Fa” might be added as the basic color name for the 12th of Thailand.