The purpose of this research is to study assessment of safety in construction of building projects. The safety assessment form was developed by referring to the Ministerial Regulations. The safety assessment composed of 8 categories: (1) construction site perimeter (2) electricity and fire protection (3) crane (4) passenger lift and material hoist (5) welding (6) fall protection (7) temporary scaffolding and stairs and (8) personal protective equipment. Based on the safety assessment of the construction site the size of the large building exceeds 2000 m2 and height exceeds 23.00 m. in the Bangkok metropolitan has of 20 buildings. The average of safety is 80 percent. By construction site perimeter the highest average and the fall protection has the lowest mean. So all parties involved workers contractors and project owner in particular need to focus on safety work to prevention against falls from high in order to reduce the loss of property life company reputation including the morale of the work as well.

The purpose of this research is to study the construction safety system for working at height. The safety system for working at height in this research is predetermined by department of labour protection and welfare and safety and health at work promotion association (Thailand). The safety system composed of (1) safety policy (2) safety organization (3) prevention measure (4) risk analysis (5) training (6) safety inspection (7) accident report and (8) emergency planning.