Giroud got the Gunners off to the perfect start after five minutes when he rifled home a first-time shot, which flew in off the keeper, in what was the Frenchman's first touch of the game.
The visitors were enjoying plenty of possession and should have doubled their lead when Lukas Podolski's shot struck the post, with the Vietnamese keeper showing fine awareness to block Alex Oxlade-Chamberlain's follow-up.
But Arsene Wenger's side did double their advantage two minutes before the interval when Carl Jenkinson's cross into the box was only half-cleared and Giroud was on hand to fire a first-time shot into the roof of the net.
And the Frenchman wasn't finished there as he deftly dinked a throughball over the advancing keeper to make it 3-0 seconds before the half-time whistle blew.
The Gunners made a raft of substitutions during the interval but it was one of Arsenal's starters who made it 4-0 when Oxlade-Chamberlain curled home a fine finish into the roof of the net from outside the area after 46 minutes.
Gunners teenager Chuba Akpom then showed his potential by netting a quick-fire double (56 & 58), first curling home following an Aaron Ramsey throughball, then tapping into an empty net at the end of a trademark Gunners one-touch move.
Spanish youngster Ignasi Miquel then made it 7-0 on 75 minutes when he drilled a low shot into the corner at the end of another flowing move.
But minutes later, there was jubilation around the ground when Vietnam netted a consolation goal after Tran Manh Dung's mistimed volley looped over substitute goalkeeper Damian Martinez and into an unguarded net (78).
Vietnam were reduced to 10 men in the closing stages when substitute keeper Nguyen Ngoc rushed from his goal and prevented a goalscoring opportunity with his hands a good 20 yards outside his area.
Wenger's side were unable to add to their tally as the full-time whistle blew to make it 14 goals in two games on their Far East tour.