This article aims to explain the causes and effects of incompatibility between public bus services (provided by the Thai government) and the needs of passengers, particularly transport-disadvantaged passengers (namely children, elders, pregnant women, persons with wheelchair, mobility, hearing or visual impairment, people carrying heavy loads, the overweight, people with slow moving preferences). A documentary-research approach on Thai official documents, international and national academic papers is utilised for critical analysis. The findings show that even though the Thai government has planned to provide low floor public buses to facilitate passengers, the services remain challenging because of inaccessibility. The universal design concept provides for full installation of all aid tools that accommodate all groups of passengers. The article provides an overview of public bus services in Thailand, discusses the meaning of ‘accessibility,’ the causes and effects of incompatibility between public bus services and passengers’ needs, the multiple advantages of accessible public bus services for all, and concludes with recommendations.