After being beaten 4-2 by Myanmar in their previous game, Garuda Muda had to produce a strong result to stay in contention for a medal, and they did not disappoint.
Zein Al Haddad's side dominated the early going and after 12 minutes, they got their reward.
Muchlis Hadi opened the scoring when he steered Adam Alis Setyano's low cross past goalkeeper Um Serei Rath, who had denied him the minute before.
Their advantage was doubled in the 37th minute when Ahmad Nufiandani headed home from close range, and the score remained unchanged for the remainder of the half.
Cambodia pulled one back shortly after the half-time break through a penalty from Prak Many Udom, but that was as good as it god for them.
The 18-year-old Muchlis added his second of the night in 67th minute, before completing his hat-trick moment later with a header that had rebounded off the post.
Evan Dimas Darmono and substitute Wawan Pebriyanto then compounded Cambodia's misery when they found the back of the net in the closing stages of the match.
"The players didn't play well against Myanmar but today, they did," Al Haddad said.
"We are happy, because we now have a chance of reaching the semi-finals."