The QueenSirikit Botanic Garden (QSBG) isvital for plant diversity conservation and ecological services for thesurrounding communities. This study aimed to investigate theforest dynamics and tree distribution patterns in a 100 × 100 m2 permanent plotof deciduous dipterocarp forest (DDF). Afive-year period, between 2012 and 2017 was examined todetermine changes in forest dynamics. All trees with a circumferenceat breast height of 14 cm or greater were tagged, measured and identified. The study revealed an increase in the number of species from 39 to 40 species. The three most dominant species,according to importance value, were Pentacme siamensis, Castanopsis argyrophylla and Dipterocarpus obtusifolius, respectively. The forest dynamics during the study period demonstrated a slight increase in the Shannon-Wiener index (H´) from 3.06 to 3.08. The net recruitment rate (1.99%/year) was found to be higher than the mortality rate (0.77%/year). The distribution pattern, based on Morisita’sindex, revealed that most of the dominant species exhibited a clumped pattern. In summary, this study offers information on diversity, dynamics and distribution patterns of DDF in QSBG, which can aid in conservation and management strategies.