I initially thought the movie's actual title is without the word KUNG but given the filipino movie's flair for dramatic impact in their titles they may have opted to used it with KUNG. Also, movie titles along with songs have poetic license to use words as they see fit. Besides, it's based on a komiks novel, maybe Gilda Olvidado should give her two cents.
And possibly the reason why the song started with "Mahawi man ang ulap, 'di mo matitiyak."