The research is about the Factors affecting team work efficiency of employees Electricity Generating Authority of Thailand case study division of land transport, to studies on following objectives: 1. Study of personal factors. The main elements of the team.The internal control system. And effective teamwork worker land transport. Electricity Generating Authority of Thailand 2.to identify personal factors. The impact on performance is a team worker land transport. Electricity Generating Authority of Thailand 3.to study the composition of the team. The impact on performance is a team worker land transport. Electricity Generating Authority of Thailand 4.to study the system of internal control that affect teamwork worker land transport. Electricity Generating Authority of Thailand .The sample A worker in the Land Transport Division. The Electricity Generating Authority of Thailand 140 people and analyzed by frequency, percentage, average, standard deviation, t - test, One - way ANOVA and Simple Regression.