his paper presents a time series regression model to estimate annual passenger demand for the State Railway of Thailand (SRT). The model was developed for a time period of 15 years (1974–1988), incorporating such variables as the country's gross domestic product (GDP), SRT passenger fares, competing intercity bus fares, and a dummy variable of the Fifth National Five Year Plan advocating a railway-favored modal shift policy. This simple but useful model analysis estimated the demand elasticities as: 0.907 with respect to real GDP; -0.970 with respect to real SRT fare; and 0.808 with respect to real bus fare. Remarkable manufacturing-oriented economic development of Thailand in recent years played an important part in recent SRT demand increases. As the relatively high own and cross fare elasticity estimates imply, the SRT is concerned about demand loss to competing intercity bus services, and has thus been keeping fare levels low. The model analysis also estimated a demand gain of 12.3% due to the modal shift policy during the Fifth Plan period, suggesting effectiveness of the policy.