Khalid Al-Hajri scored the solitary goal of the match after halftime to hand Oman their third win in nine Group B matches.
It was an evenly contested first half with few chances created by both sides.
Oman got the first shot on goal after 12 minutes with Khalid Al-Hajri blasting a powerful strike from outside the box, only to see it comfortably blocked by goalkeeper Nguyen Manh.
Eight minutes later, Zahir Al Aghbari drove a dipping shot across keeper Nguyen Manh, but it went wide at the far post.
Vietnam deployed several attacks towards the Omani goal, but failed to produce real threats, excluding an easily handled volley by Nguyen Quang Hai.
The Golden Star Warriors produced a strong start to the second half, with substitute Nguyen Cong Phuong threatening to score with a straight cornerkick in the 57th minute which was thwarted by goalkeeper Ibrahim Al Mukhaini.
Photo: NDO/Tran Hai
Oman broke the deadlock five minutes after the hour mark when unmarked Al Hajri jumped up to power in an unstoppable header from a corner kick.
The following minutes saw the hosts push hard for an equaliser.
Vietnam should have restored the parity in the 76th minute when they were awarded a freekick from 25 metres, but Quang Hai’s powerful left-footed strike could not beat Ibrahim Al Mukhaini.
Park’s side created some more chances with time running out, but attempts by Nguyen Cong Phuong and Pham Tuan Hai were off target.
As scheduled, Vietnam will play their last World Cup qualifying match away against Japan on March 29.
