Background and objectives Variation in composition and functionality of glutinous rice starch greatly affects their industrial application. This study examined the starch compositional, structural, and functional variability among five Thai glutinous rice cultivars, and the effect of molecular structure and composition on starch functionality was pinpointed. Findings Amylose content, amylopectin chain‐length distribution (CLD), and relative crystallinity were not different among the cultivars (p ≤ .05), whereas RD14 possessed largest mean granule diameter. Conclusion temperature of gelatinization and peak viscosity (PV) were lowest in RD6 and RD10, respectively, while RD6, RD10, and RD14 had lower breakdown (BD) compared to others. Despite small variation within each parameter, multivariate analysis revealed the distinct characteristic of waxy donor, RD6, and RD10 compared to others. Proportion of amylopectin B1 chains and granule size showed negative correlation (r > 0.5) with PV and BD, respectively, whereas proportion of amylopectin B2 chains positively correlated (r > 0.5) with PV and final viscosity (FV). Conclusion Amylopectin CLD and starch granule size were the key factors determining starch pasting properties among these waxy rice genotypes. Significance and novelty Variations in composition, structure, and properties of Thai glutinous rice starches were observed, which could be adopted for a diverse array of end uses.