Before the club announced Phuong was joining, their Facebook page had around 31,000 followers, but the figure is now more than 75,000.
Comments by Belgian supporters are sometimes overshadowed by the sheer number of comments coming from Vietnam.
"We have to find a good balance between our Belgian and Vietnamese fan bases," Fiorenzo Mostien, Sint-Truidense’s communications officer, said in an interview with national broadcaster Vietnam Television.
The club are considering hiring a Vietnamese-speaking person to support their communications office, firstly to receive comments from Vietnamese fans on Facebook and Instagram and respond when necessary.
Speaking to the Belgian media, Mostien said the club’s fan base has not only grown online.
At a practice match against Lommel SK, there were around 50 Vietnamese supporters in the stands.
"Most fans come from Germany. We assume that we will be able to welcome even more Vietnamese fans during the competition. The press interest from Vietnam is also starting to increase. Soon we will get one of the largest TV channels from the Asian country for a real report."
Mostien also shared some of his thoughts on Phuong, who went from being a superstar in his home country to a relative unknown on the streets of Sint-Truidense: "It was, of course, adjustment. You see that he feels better and better every day. He joined the team later and therefore still has some work ahead, but we expect that he will be in top shape soon. Our coach Marc Brys naturally takes care of that.
Cong Phuong is a big superstar in Vietnam, but not everyone knows him in Europe."
Phuong said he would need to improve his skills and learn to get along with his teammates. "There’s a lot for me to learn."
Phuong made his Jupiler Pro League debut on Friday when he came off the bench in the 70th minute. The club lost 6 - 0 to Club Brugge.
Phuong and his fans will no doubt be hoping he can make as big an impact on the pitch as he has on social media.
The 24-year-old striker was the biggest influencer in social media in Vietnam in June, with him featured in 525,983 posts and comments, according to statistics from analytics website Buzzmetrics.