The moisture buffering capacity of wooden building envelopes plays a significant role in regulating indoor humidity and influencing energy consumption, particularly in hot-humid climates. This study examines the hygrothermal performance of traditional pile-dwelling structures in northern Guangxi, comparing two surface finishing conditions: painted and unpainted walls. Using the dynamic simulation tool WUFI Plus, a representative building model was developed and evaluated under both natural ventilation and HVAC-controlled scenarios. The results indicate that surface painting substantially diminishes the moisture buffering capacity of walls, leading to greater fluctuations in indoor relative humidity. While painted walls slightly reduce dehumidification loads by limiting vapor transmission, they also increase cooling energy demand by 6.96%. Seasonal variations in moisture transfer were also observed, with buffering effects more pronounced in summer than in winter. These findings highlight the importance of carefully considering wall surface treatments to enhance indoor comfort and optimize energy efficiency in wooden buildings exposed to hot-humid conditions.