The genetic relationship among cassumunar gingers (Zingiber cassumunar) in Thailand was assessed by amplified fragment length polymorphism (AFLP). Twelve AFLP primer combinations generated a total of 309 fragments, of which, 242 bands were polymorphic with an average of 20.2 bands per primer pair. Genetic similarities were obtained using Jaccard similarity coefficients, and a phylogenetic tree was constructed using the UPGMA clustering method. Pairwise similarity estimated between cassumunar gingers ranged from 0.7644 to 1.00 with an average of 0.879. Cluster analysis divided the samples into five groups with a high co-phenetic correlation value (r = 0.99). Genetic variability within and among collection regions was estimated by analysis of molecular variance (AMOVA). High molecular variance (84%) was found within samples from the same region. The results implied dispersal of plant materials between collection regions. The genetic similarity assessed by AFLP showed that there are duplicate accessions in the germplasm collection. This genetic information is very useful for germplasm maintenance and a crop improvement program.