This study is an attempt to test a framework that looks into how relationships in internal and external logistics factors contribute to the success of firms in the Electrical and Electronics Industry in Thailand. Data were collected from the 303 firms in the Electrical and Electronics Industry in Thailand during 2009. The analysis is divided into two studies. In the first study, all responding firms are included in the analysis. In the second study, the analysis is divided into two scenarios based on the firm’s capital investment (less than or higher than 200 million Baht). Questionnaires were used as a tool to collect data and Structural Equation Modeling (SEM) was used to analyze relationships among these factors. Seven hypothesized relationships were tested on five factors which consisted of human resource management, logistics infrastructure, internal operational activities, external operational activities and business performance. The results showed some supports for some of the hypotheses and made a contribution to the understanding of the influence of internal and external logistics factors on business performance based on the size of the firms.