Is this happening when the air/con is in operation or when the air/con is off?
Air/con units are by default dehumidifiers. You will typically see water dripping off one of the roof corners when the air/con is running.
The unit blows humid interior air over the evaporator (inside radiator looking part) which is cold. Just like a cold glass of ice tea, water will condense out of the air onto the evaporator. It then will drip down into a metal pan which has a hose allowing the water to run out onto the roof and to the ground. If the hose gets clogged, the water will fill the pan and overflow...resulting in dripping inside.
A dehumidifier works essentially the same way except the condenser (outside radiator looking part) is also on the inside. The air blows over the evaporator, cooling and dehumidifying and the over the condenser which reheats the air. Because there is additional heat generated by the electric motors, you get a net increase in heat inside.
If it's dripping when the air/con is off (and presumably raining), you most likely have a leak.