All three of South China's goals came in the first half. Lo Kong-Wai opened the scoring in the 13th minute and Mahama Awal made it 2-0 just six minutes later.
South China went 3-0 up in the 38th minute when new recruit Daniel McBreen headed the ball into the back of the net with tremendous force.
However, the Hong Kong-based team were denied a clean sheet as Zaw Lin Tun scored a consolation goal in the 88th minute.
Thanks to this win and their 6-1 mauling of Philippines side Global on February 25, South China now sit comfortably atop the Group G standings.
But, Gomez reiterated that he does not want his side to take their foot off the pedal, especially since they will be playing Malaysian side Pahang next Wednesday in Kuantan.
"We have won two matches but the most important thing is for the team to keep improving," Gomez told the South China Morning Post. "We will have to travel to Malaysia for a crucial game against Pahang next week and a hectic schedule in domestic competitions may also affect our players."
Meanwhile, Yadanarbon coach Kyi Naing blamed his side's poor performance on the rainy weather and chilly winds.
He added that his side could not run properly since they were not wearing the right type of boots.
Despite his excuses, Naing has not given up on his side's AFC Cup campaign.
"If we can beat Penang, we still have a chance in the group," he said.