Giroud, who had scored a brace in the Gunners' 7-0 romp over an Indonesian Dream Team at the weekend, put the tourists ahead inside five minutes after collecting a pass from Tomas Rosicky.
Arsenal - with Bacary Sagna deployed at centre-half - had to wait until just before the break to further extend their lead, as Lukas Podolski saw an effort chalked out for offside and then hit the post.
Giroud eventually made it 2-0 after 44 minutes, and then completed his treble with another neat finish from Alex Oxlade-Chamberlain's pass after Anh Duc had missed the home side's best chance.
Following the restart, England midfielder Oxlade-Chamberlain slotted in number four after being set-up by Theo Walcott.
After a number of anticipated substitutions, England under-19 international Chuba Akpom scored a quickfire double (56, 59), the 17-year-old having replaced Giroud.
England midfielder Jack Wilshere then made his first appearance of the tour after he came on for Oxlade-Chamberlain just after the hour mark.
With 15 minutes left, defender Ignasi Miquel converted number seven after a powerful run and cross from attacking German midfielder Thomas Eisfeld.
The fanatical home crowd finally had something to cheer when Tran Manh Dung's effort looped up over substitute goalkeeper Damian Martinez, before the closing stages were played out in a thunderstorm.
There was still time for Vietnam goalkeeper Tran Buu Ngoc to be shown a red card after he handled outside his area as Wilshere ran clear on goal.
Source: DSG
Source: DSG