The trend of travel in secondary cities is growing among Thai people especially Generation Y. This trend is a result of the campaigns of the Tourism Authority of Thailand (TAT) cam which is targets Thai Generation Y. With their purchasing power, the accommodation in the secondary cities has been significantly grown and expanded to support the demand of this group. This study aims to understand customers’ behaviors and influencing factors towards booking accommodations in the secondary cities of Thailand by using the five-stage model of the buying decision process. The result shows that most of Generation Y search and book for accommodation in secondary cities via online travel agency e.g. Agoda, Booking, Traveloka, etc. On the evaluation of the alternative stage, the attributes that Generation Y focuses on are cleanliness, location, and the picture of the accommodation. For the influence factor that impacts Generation Y in making a decision is the review from the previous customer, rating score and review from acquaintances