d*mn! I found the problem dy...
it's inside the headlamp... I tried troubleshooting myself.. found a fuse blown, and it's the Left-side beams fuse. (15A)
replaced another one, still blow... aargghh... so I open up the headlamp cover, when changing bulbs one la...
OMG! the parking lights wire melted on the metal, 'short-ed' on the metal, which causes the short-circuit, forcing the high beam to turn on.
And I found that the wires inside all are in terrible consider... the rubber insulators all are cracked and worn out already... :(