I have a KS-602H smart switch. In the box said the imput voltaje is 110v-125v, in my country we use 220v, I connected the smart switch and work without problems…do someone know why the smart switch work well and this one dont burn?
Is safe keep the smart switch working in 220v?
It is very smart of you to ask. No, it is not safe.
The device will burn out eventually, the only question is whether it electrocutes a person before it does. 
Only install electrical equipment, even a light switch, on circuits it is a safety-rated for.