"Do you need a little beat?" Obama asked her. "Go ahead, c'mon."
"Vietnam or English?" she asked.
"In Vietnamese, of course, but I won't know what it means," the president replied.
The woman complied and busted out a few bars, getting the audience of 800 young people to clap along with her. She later told the president that the rap was about people with money and big houses not being happy.
The rapper was later revealed to be 26-year-old Hàng Lâm Trang Anh, a performer known here by her stage name Suboi and considered by some to be the nation's "queen of hip hop."