The objective of this study was to investigate the genetic variability among 43 Thai upland rice genotypes and to estimate the broad-sense heritability for the examined traits. The genetic variability and diversity studies provide important information for plant breeders who manage breeding programs. Forty-three upland rice genotypes in Thailand were assessed for the genetic variability using randomized complete block designs with three replications in two years at the Faculty of Natural Resources, Prince of Songkla University. The seven characterized quantitative traits showed significant variations by genotypes, except rice yield. For the interaction between Genotype and Year was significant for days to maturity, plant height, number of tillers hill[1]1 , rice yield, and thousand grain weight. High genetic coefficients of variation were observed for days to flowering, plant height, number of tillers hill-1 , thousand grain weight, and grain width. High broad-sense heritability was found for days to flowering, days to maturity, plant height, number of tillers hill-1 , thousand grain weight, grain width, and grain length. The cluster analysis grouped the 43 genotypes into eight groups based on SSR markers at 0.75 similarity level. These results show that the large variability will help rice breeders in selecting the appropriate genotypes for future breeding programs.