Seasonally dry tropical forests (SDTFs) are a major component of Southeast Asian Forest landscapes and play a vital role in regional carbon cycling, yet long-term data on their dynamics and productivity remain limited. This study quantified aboveground biomass (AGB), forest dynamics including mortality and recruitment rate, and aboveground net primary productivity (ANPP) across three SDTF types—deciduous, semi-evergreen, and evergreen forests—at the Khun Ream Forest Research Station in Siem Reap Province, Cambodia, based on four years of monitoring (2021–2025). Permanent 1-ha plots were established in each forest type, where all trees ≥5 cm DBH were measured annually and litterfall was collected monthly. Litterfall production in each plot was quantified using 25 traps of 0.49‒0.50 m2 surface area. AGB differed significantly among forest types, with the highest values in semi-evergreen forest (145.7 ± 2.2 Mg ha⁻¹), followed by evergreen (124.4 ± 7.4 Mg ha⁻¹) and deciduous forests (79.9 ± 1.7 Mg ha⁻¹). Although tree mortality rates were comparable among forest types (1.02–2.59% yr⁻¹), temporal variability was documented, particularly in evergreen forest, where wind disturbance may cause substantial biomass loss. In contrast, recruitment rates were significantly higher in deciduous forest (9.13 ± 2.09% yr⁻¹) than other two forests (4.11–4.25% yr⁻¹), indicating rapid stand turnover. Despite structural and demographic differences, ANPP did not differ significantly among forest types, averaging 6.72–9.99 Mg ha⁻¹ yr⁻¹. Semi-evergreen forest exhibited a peak ANPP of 16.35 Mg ha⁻¹ yr⁻¹, exceeding previously reported values for Cambodian SDTFs. These results highlight that episodic disturbances and climatic variability strongly regulate productivity in the region. Our findings demonstrate that different SDTF types in Cambodia maintain comparable carbon sequestration functions, while semi-evergreen forests emerge as key carbon reservoirs. This study provides rare long-term evidence from Cambodian SDTFs, contributing to improved understanding of SDTF resilience under climate change.