Danny Welbeck, Chris Smalling, Fabio Da Silva and substitute Adnan Januzaj put United 4-0 up after 49 minutes, but they took their foot off the pedal and plucky Kitchee gave the scoreline some respectability with two fine goals on a humid but dry night.
Substitute Jesse Lingard put the gloss on a satisfactory evening for United with a lovely curled shot with 10 minutes left.
After a tentative start, United took the lead on 16 minutes, and there was a fair bit of luck in it. An Ashley Young volley struck a post via a deflection, only to fall into the path of Welbeck, who smashed the ball home.
Three minutes later Wilfried Zaha blazed wildly over as the chances came thick and fast for United, who started with Robin van Persie, Ryan Giggs and Rio Ferdinand on the bench at the sell-out 40,000 Hong Kong Stadium.
Van Persie was introduced with 10 minutes left, to howls of approval from the locals.
Moyes, who took over from Alex Ferguson on July 1, had admitted that he was concerned about the pitch, which had cut up badly during last week’s Barclays Asia Trophy after days of torrential rain.
But United made light of the poor surface against dogged opposition.
On 22 minutes it was 2-0, defender Smalling rising highest to nod in a pinpoint Tom Cleverley cross.
Full-back Fabio, who was farmed out to QPR last season, then got in on the act, drilling a low drive into the bottom corner after a clever reverse pass from Zaha.
It was 4-0 on 49 minutes, Januzaj heading in from a cross by Alexander Buttner, who had also come on at the break.
Kitchee pulled one back on 53 minutes, and it was a beauty, with Lam Ka-wai curling into the top corner from outside the box, giving reserve United keeper Ben Amos no chance.
And Kitchee repeated the trick on 68 minutes as Alex Alkande turned Smalling inside out before firing in.
Before arriving in Hong Kong, United had won one, drawn one and lost two in their pre-season tour that also took in Thailand, Australia and Japan.
Their next friendly is on August 6 in Sweden, where striker Wayne Rooney — subject of a bid from rivals Chelsea — is expected to make his return from a three-week injury lay-off.