Initially, passenger vans in Bangkok were illegal. However, passengers preferred them to conventional buses due to their speed, comfort and ease of access at affordable prices. Conventional bus operators considered the passenger vans as competitors who caused lower revenues. Therefore, Thai government started enforcing passenger van regulations in 1999 to provide safe public transport and to eliminate competition. This policy was not based on theoretical consideration. An analysis of passenger vans market in Bangkok has not been undertaken. Moreover, illegal passenger vans are still existent. This study verified market competition between passenger vans and conventional buses based on demand side and found that there was no price competition. The passenger van market is an oligopoly market with implication of product differentiation. Deregulation of passenger ban entry was recommended to bring more licensed passenger vans and to create competitive market environments where services would be improved. Regulations related to safety and qualities of the services were maintained.