On Monday, Facebook account MS PUIYI posted two photos of a woman wearing ao dai and releasing colorful lanterns on the Hoai River in Hoi An, a UNESCO heritage site and popular tourist destination. However, she did not wear the long flared bottoms that go with the dress.
The post quickly attracted 21,000 likes and 600 shares, with many Vietnamese netizens decrying it as "immodest" and "disrespectful" while asking the Facebook account owner to remove the images.
"Modern sexy is not wrong, but you are wrong to take the Ao Dai, the national dress of Vietnam, I absolutely do not accept it. I think you should delete this photo, Vietnamese people will be very angry because of this," a Facebook user commented.
Another user wrote ao dai is the traditional costume of the women of Vietnam. "We welcome international friends to come and wear this national costume. But your style really doesn't match the national costume.
"I hope you can take down the post and apologize to us for disrespecting this country's culture."
Ms Puiyi or Siew Pui Yi is an internet celebrity from Malaysia. Her Facebook has over 615,000 followers and her Instagram, over 17.3 million.
On Tuesday, Tong Quoc Hung, head of the Culture and Information Department of Hoi An, said local authorities are seeking to remind her about Vietnamese culture and traditional customs.
"The female tourist revealing her underwear in the ancient town of Hoi An is offensive, said Hung, adding that Hoi An culture has not allowed it for a long time.
"The image of the female tourist does not match the customs and habits of the people here."
Under current Vietnamese law, using profanity, swearing, wearing offensive or revealing clothes at festivals could attract fines up to VND500,000 ($21.88).
This was not the first time foreign celebrities had triggered public outcry in Vietnam for wearing traditional Vietnamese dress with cultural faux pas.
In 2019, American country singer Kacey Musgraves wearing Vietnam’s traditional dress without its long trousers performed in front of thousands of fans at a concert.
The ao dai has for long been an icon of Vietnamese culture, praised for highlighting the graceful beauty of Vietnamese women.