A PA (or Public Address) System is an audio system used in a building for emergency announcements or in some cases to also play background music. In some installations the PA system is connected to the fire alarm system so that during a fire the PA system will broadcast an emergency evacuation message automatically.
The Cambodia fire code("Fire Safety Systems - Building Design Code" of 2019) states that public places in high rise residential buildings shall have a pre-recorded voice warming system or emergency broadcast system install (part 12.4.1(15)). You may also want to install a PA system to play background music and make occasional announcements such as in a large store.
Based on your requirements we can design a system to suit your needs and cost.