Khoa entered the field as a substitution in the third additional minute of the second half. Just a minute later, he shoved Pham Minh Nghia as the Nam Dinh player cleared the ball. An unhappy Hung then had some words with Khoa.
In response, Khoa punched him in the face, leading to an altercation. Referee Nguyen Manh Hai subsequently gave Khoa a red card and Hung a yellow.
Khoa angered many Nam Dinh fans who drowned him in insults, necessitating his secure removal from the field.
For his violent behavior, Khoa is expected to receive a punishment from Vietnam Football Federation in the coming days.
The game ended with a 2-1 victory for Nam Dinh, which helped them climb to 11th while HCMC dropped to 12th, right above bottom-placed Sai Gon FC.