Paul Ng takes his job as a police officer very seriously, especially in Asian division of the LAPD. He is familiar with Chinese cultures and Chinese societies, and with Chinese gangs, including the Triads.
Ng was in his office with his partner when Martin Riggs and Roger Murtaugh come in to learn more about the boat filled with Chinese slaves and who is responsible. Ng reveals to the duo a man named Uncle Benny Chan is the one who illegally brought the slaves to Los Angeles and operates a nightclub and restaurant in Chinatown.
He is later seen again at the site where the counterfeit money was being made. When Murtaugh tells him and his partner about Uncle Benny mentioning something about the Four Fathers, Ng reveals to the duo the Four Fathers were leaders of the Triads before they ended up becoming incarcerated. Ng and his partner join Riggs, Murtaugh, and Lee Butters and some other officers at the pier as they show the Chinese General the money about to be presented to him is counterfeit. A shootout begins between the Triad and the general and his men. Ng and all the others responds with firepower. During the shootout, Butters gets shot and wounded while protecting Murtaugh, and Ng provides support for him by getting an ambulance and taking him to a hospital.