Ceiling LED light emits very dim light when switch is off!
There are two typical reasons for this:


The Phosphorous used in the led is experiencing chemiluminescence, a cold chemical reaction that produces light. The Phosphor is normally used to be give leds their white color through photo luminescent reaction, reacting to photons of a different wavelength, but it can glow in the dark without that.
The light bulb is on a circuit with a switched neutral wire, instead of a switched hot wire. This means that the AC voltage on the hot wire can still slightly power the leds and/or the capacitors in the light bulb, leading to a few milli or micro amps of current to flow through ultra efficient leds, lighting them up.


You could test this by putting the bulb in a switched lamp with a non-polarized power connector plugged in one way, and then flip the connector around the other way. One way should result in completely off leds.