The potential of sustainable energy in Thailand's bank is studied in term of energy efficiency and environmental aspect. The achieved national regulations for buildings in Thailand, such as building code and green building, are the guideline to set up the optimal energy policy. Therefore, the banking recognizes the importance of the energy policy with business condition. According to the various bank in Thailand, the advertising and promotion of bank is very important for increasing the market share, so the sign lighting system is the first sign of bank which are needed to install without energy concern. For small and medium sizes of bank in Thailand (approximate 4,000 building), more than one third of lighting system is sign lighting which is proposed only advertising objective. This paper introduces the optimal energy management of sign lighting to reduce the energy consumption without effect to the advertising objective, which remained the illumination need and acceptable investment of sign lighting. In addition, two technologies of the sign lighting system for advertising are proposed to evaluate the energy performance, which are T5 fluorescent lamps with electronic ballast and Light Emitting Diode (LED) lamps compare to the existing system with T8 fluorescent lamp and low loss ballast. The experimental results show that the LED lamps sign lighting can reduce the energy consumption more than 50% with the significant feasibility in practical implementation. Finally, the environment aspect will be presented in term of CO2 reduction and the barriers of LED lamps sign lighting will be concluded. © 2011 IEEE.