Face mask usage is one of the preventive measures encouraged worldwide to limit the transmission of the SARS-Cov-2 pandemic. Hence, production and mass use of face masks is on the rise due to the pandemic as well as government rules that mandate citizens to wear face masks. However, the improper disposal of face masks has been polluting the environment with enormous hazardous waste. In this study, a face mask littering assessment in an urbanized environment, Bangkok, was carried out. Three streets in the city were selected and observed for face mask littering for 5 h per day for 42 days. Moreover, a questionnaire from 605 participants was recorded to determine mask handling and disposal practices. The study found a total of 170 single-use face masks within a 13.30 km path. Furthermore, the highest (40) and lowest (17) cumulative litter were recorded on Sunday and Monday, respectively. Buffer analysis at 300 m showed 47% of mask litter was found within five mass transit stations, while 15% are within a single street market. Of 605 respondents, 82.15% used a single-use face mask. Surprisingly, most of them (70.58%) disposed of used face masks in regular bins along with their household waste. The results highlight three policy implications to tackle the growing problem: raising awareness, regulation, and provision of bins designed for used face masks in strategic places and supporting innovations and research for eco-friendly face masks.