A light emitting diode (LED) lamp assembly comprises an LED string and a plug. The LED string comprises multiple LEDs connected together in series. The plug is connected to the LED string and an external AC power source and has a circuit board. The circuit board is mounted in the plug, turns the LED string on or off, converts AC power to DC power and comprises an AC/DC circuit, a control circuit and a switch circuit. The AC/DC circuit is connected to the external AC power source and the LED string and converts AC power to DC power to provide operating power for the LEDs. The control circuit is connected to the AC/DC circuit to regulate illumination of the LEDs. The switch circuit is connected between the LED string and the AC/DC circuit and is controlled by the control circuit to turn the LEDs on or off.