A Vertical stratification of the bird assemblage between abandoned settlement areas (ASA) and dry evergreen forests (DEF) was investigated in the western forest complex of Thailand, Natural World Heritage Site. The aim was to examine species diversity, vertical strata patterns, and niche breath of individual bird species between disturbance and primary forests. A permanent line transect was used for the field survey. Our research presents the results of a first study on vertical stratification of bird assemblages between abandoned settlement areas and primary forests in Thailand. The study revealed 170 bird species. Diversity indices of vertical strata in the ASA tended to be lower than those in the DEF sites. However, the bird community in the DEF and ASA was classified into 3 major groups: ground level group, lower canopy group (1-5 m in the ASA and 1-15 m in the DEF) and upper canopy group (5->25 m in the ASA and 15->25 m in the DEF). Most species were relatively generalized in their behavior and used resources across broad ranges of microhabitatas. The study also demonstrated that the ASA appeared to support less species richness than the DEF. The results of this study provide vital information in revealing patterns of assemblage structure and majors factors in the maintenance of species diversity. Further research should concentrate on these species to determine resource use pattern, and investigate the effect of forest fragmentation on their movements. Furthermore, this study deonstrated that bird diversity showed a clear recovery pattern after human resettlement. Recommendations are given to limit human disturbances as much as possible to allow for maximum avian diversity to recover.