Biomass burning (BB) frequently occurs in SouthEast Asia (SEA), which significantly affects the air quality and could consequently lead to adverse health effects. The aim of this study was to characterize particulate matter (PM) and black carbon (BC) emitted from BB source regions in SEA and their potential of deposition in the alveolar region of human lungs. A 31-day characterization of PM profiling was conducted at the Doi Ang Khang (DAK) meteorology station in northern Thailand in March 2013. Substantial numbers of PM (10147 ± 5800 # cm–3) with a geometric mean diameter (GMD) of 114.4 ± 9.2 nm were found at the study site. The PM of less than 2.5 μm in aerodynamic diameter (PM2.5) hourly-average mass concentration was 78.0 ± 34.5 μg m–3, whereas the black carbon (BC) mass concentration was 4.4 ± 2.6 μg m–3. Notably, high concentrations of nanoparticle surface area (100.5 ± 54.6 μm2 cm–3) emitted from biomass burning can be inhaled into the human alveolar region. Significant correlations with fire counts within different ranges around DAK were found for particle number, the surface area concentration of alveolar deposition, and BC. In conclusion, biomass burning is an important PM source in SEA, particularly nanoparticles, which has high potency to be inhaled into the lung environment and interact with alveolar cells, leading to adverse respiratory effects. The fire counts within 100 to 150 km shows the highest Pearson's r for particle number and surface area concentration. It suggests 12 to 24 hr could be a fair time scale for initial aging process of BB aerosols. Importantly, the people lives in this region could have higher risk for PM exposure.