The purpose of the study is to investigate internal and external factors influencing the use of social networking sites (SNSs) in Thailand. Overall (N = 451) participated in this study. Survey research was employed to examine the interrelationships and differences among a set of variables. The results showed that both internal and external factors affecting the use of SNSs and SNS motivation. External factors, particularly media and significant others were more influential than internal factors to predicting time spent on SNSs. People who were influenced by media and significant others would be more likely to spend more time using SNSs and Facebook. SNS motivation led to different SNS use. In particular, those who were motivated to use SNS for relaxation would spend more time using Facebook. In addition, the findings indicated that females would spend more time using YouTube, Twitter, and Hi5 than males. Moreover, females tended more to use SNSs to maintain their friendship than did males. © 2013 Elsevier B.V. All rights reserved.