The president received a huge cheer as he took to the stage in a one-party authoritarian state where politics is opaque and young people’s voices are rarely heard.
Suboi, one of the country’s best known female rap artists, serenaded Obama with Vietnamese lyrics about whether people are really happy if they have lots of money.
Seemingly delighted with the exchange, Obama praised the journey of hip-hop “which started out as an expression of poor African Americans” and became a “global phenomenon”.
He then appeared to take a thinly veiled swipe at Vietnam’s authoritarian leaders, who regularly suppress critical artists.
“Imagine if at the time when rap was starting off our government had said ‘No’ because some of the things you say are offensive, or some of the lyrics are rude, or you’re cursing too much?” he said.
“If you try to suppress the arts then you are suppressing the deepest dreams and aspirations of a people,” he added.
Earlier another young man began his question with: “Mr President, you’re so handsome.”
To which Obama quickly quipped “Oh. You can just stop there if you want.”
– Dreaming of a father –
Another asked whether Internet posts about Obama’s alleged marijuana smoking as a youth were true.
“I don’t know if that’s true,” Obama quickly remarked, further dousing the issue with a warning: “Don’t believe everything you read on the Internet.”
But that particular exchange also prompted some soul-searching from Obama about leadership and growing out of a rebellious teenage phase prompted by the absence of a father.
“As I got older I realised that instead of worrying about the father who wasn’t there, I should start worrying more about what can I do to take more responsibility for my own life,” he added.
The environment was a subject that repeatedly came up. Vietnam is acutely vulnerable to climate change and environmental causes have been the focus of numerous protests against the authorities, especially among young people.
Obama said he recognised the freedom western industrialised countries have had to pollute the earth for far longer than developing ones, but urged all countries to work together to prevent disaster.
“The problem is, if a country like China or Vietnam or India took the same development path the West did, we’re all going to be under water.”
Obama has been met with throngs of enthusiastic well-wishers in a country where politicians are notorious for their remoteness and lack of charisma.
“I like his behaviour, being the most powerful man in the world, but very close to people, not like leaders here,” said 22-year-old Tran Huu Duy. “They only wear suits and talk cliches… (they) cannot inspire young people.”