"It's a great honour and a great pleasure to be in this country," pony-tailed Beckham told the crowd in Ho Chi Minh City, Vietnam's southern commercial centre formerly known as Saigon.
The crowd roared when the 28-year-old former Manchester United midfielder balanced a ball on his head and then on his back while doing push-ups in the stadium, which was festooned with banners and flags of the player.
Manchester United games are regularly broadcast on Vietnamese television and the team attracts a strong following in country.
"I used to see him on TV. This is the first time I see him outside. I am very happy, very excited," said 22-year-old Phan Bu Trung, who was wearing a white Manchester United jersey.
Having followed the team since 1994, when he was a young teenager, Trung said he had mixed feelings about the departure of his hero to Real Madrid in a 35 million euro ($41 million) transfer.
"I cannot be happy for this but I understand this because he is a professional player."
Beckham is on a promotional tour of Asia on behalf of his commercial sponsors. In Vietnam, international media have been told they will not be allowed to cover the tour.