Do Van An, 33, is now investigated for "sex service brokering" and "harboring prostitutes."
Nguyen Huu Huy, 19, is facing the charge of "sexual services brokering," police announced Wednesday.
On the afternoon of July 5, police of Ba Dinh District inspected a hotel in Lieu Giai Ward and found a woman providing prostitution services to a man.
Police arrested An, who connected the woman prostitute with the man for the service that cost VND3.5 million (US$138).
Police found An was running a ring of 15 female prostitutes. Among them, four were under 16, and one was under 18.
Huy was identified as helping An to connect the women with customers and transporting them to hotels.
In Vietnam, prostitution is illegal.
The government treats prostitution as a social evil and has strict laws against it. Those caught engaging in prostitution can face penalties including fines and imprisonment.
Law enforcement efforts often focus on raiding brothels and arresting sex workers and clients.