In the past few years, bus and van accidents on national highways have increasingly become more severe, as witnessed by the continuously rising number of deaths and injuries in Thailand. The speeding behaviors of drivers is considered as the main factors causing bus and van accidents in Thailand. In this study, the field observation survey was conducted to observe the speeding behavior of bus and van drivers on major highways located within the 200 kilometers from Bangkok throughout the year 2013–214 and 2017 by using laser speed gun. Totally, 28 site locations that have the pedestrian overpass bridge on major highways were selected to conduct the speed data on four types of public vehicle such as public van, private van, public bus, and private bus. The overall result reveled that on average, there about 49% of bus and van drivers exceeding the speed limits, though the non-compliance with speed limits above 80% was also observed at several locations. Moreover, the prevalence of van drivers’ speeding appeared to be higher for private or rental vans (52%) compared to public van (43%). Conversely, the proportion of bus drivers exceeding speed limit seem like to be higher for public bus (49%) compared to private bus (46%). Considering the drivers speeding behavior by vehicle type and observation periods, the proportion of drivers exceeding speed limit trend to decrease in year 2017 for all type of vehicle, especially for public van (53% in 2013, 44% in 2014, and 11% in 2017). This may come from the reason that the Department of Land Transport enacted many road safety measures and regulations for public van at the beginning of the year 2017 as the result of fatal van accident which killed 25 people during the New Year 2017.