Vanuatu's Clement Mainguy won the opening rubber 6-4, 6-4 before the Northern Marianas' Colin Sinclair also won his rubber in straight sets.
The doubles pairing of Gillian Osmont of Tahiti and Brett Baudinet of the Cook Islands defeated their foes for a 3-0 win.
It was a partnership with a vast gulf in experience - Osmont was making his Davis Cup debut, Baudinet was playing in his 61st Davis Cup tie.
Pacific Oceania next play the United Arab Emirates, which lost its first match to Saudi Arabia.
Pacific Oceania's women's team have won two ties and lost one in their section of the Billie Jean King Cup, also being held in Vietnam.
The team started off with a 3-0 loss to higher ranked Thailand but bounced back with a 3-0 win over the Maldives - without the loss of a single game - and another 3-0 win, over Singapore.
They have one more group game, against Malaysia.
Photo Fijian Government Caption: Pacific Oceania tennis teams assemble for the opening ceremony