Hi Phil
That must be some thai magic , depend the ECU has no connection to the headlight circuit .
Just double check the wirering diagram .
12 V from Batterie goes to the Main Fuse on the Starter Relais and from there direct to the Ignition switch .
From the Ignition Switch it goes via Fuse 6 to the Starter Switch (lights off when the starter turn) and from there
via the Hi/low beam switch to the Headligt Bulb and back to Ground /batterie minus .
There is nothing in this circuit that can be triggered by the ECU .
There is however a connection from Pin 13 on the ECU and this Pin is connect via a diode in the ignition Switch to +12V before the ignition Contact .
This Pin 13 is in the wirering Diagram also called IMOV and that stand normaly for the imobiliser connection and thats a thing the CRF don't have .
No Idea what this connection is for or if its really there , no Info about this Connection in the Fuel injection/ECU discription , but what ever it is i see no way how this could switch the Power to the Headlight of .
What your mechanic do is reset the DTC . That is where faults of the Ignition System gets stored and shown on the MIL in the Dash as blinking Code .
But there is no Code in the DTC for Headlight fault .
There was maybe a fault from way back stored that he delete but how that effect the Headlight is a mystery to me.