Ambient nanoparticles, or PM0.1 and thirteen trace elements (Al, Ba, K, Fe, Cr, Cu, Ni, Na, Mn, Mg, Ti, Pb, and Zn) were studied in Hat Yai, Thailand during the year 2018. The annual average PM0.1 mass concentration was 8.45 ± 1.93 µg/m3. The PM0.1 levels in Hat Yai were similar to those in large cities in South East Asia, such as Hanoi and North Sumatra, but lower than other cities in Thailand. The sum of thirteen trace elements was 207.83 ± 17.06 ng/m3 and was dominated by Na, Zn, K, Mg, and Al. The highest concentration of elements occurred in the pre-monsoon season followed by the dry and monsoon seasons. A principal component analysis (PCA) indicated that PM0.1 comes from motor vehicles, crustal dust, industrial and biomass burning. The PM0.1 was dominated in the pre-monsoon season, suggesting that biomass burning from the southwest direction could cause an increase in the levels of Cr, Ti, and Ni. The total cancer risk from all the carcinogenic elements was 1.98 × 10−6 in adults, indicating that the carcinogenic risk is in a tolerable risk assessment range. The increasing levels of PM0.1 during transboundary haze pollution and local source emissions are a concern. Display omitted •Nanoparticles (NPs) bound trace elements were measured in southern Thailand.•The main sources of NPs were found to be motor vehicle, road dust, industrial and biomass fires.•The carcinogenic risk is considered to be in the tolerable risk assessment range.•Transboundary haze was found to be important during pre-monsoon season.