Vietnam is among the five biggest global markets for YouTube ( Photo by Reuters/Lucy Nicholson)

The top five markets - India, Indonesia, Japan, Thailand and Vietnam - are all Asian nations, YouTube’s Asia Pacific regional director Ajay Vidyasagar told CNBC. Ranking is based on how long users spend watching videos on the site. Vietnamese spend around seven hours a day online, of which 2.5 hours on average are spent on social media. YouTube is the second-most accessed site in the country with a user ratio of 59 percent, behind Facebook at 61 percent, according to a 2018 report by We Are Social. Mobile consumption, actually, really started showing up as a game-changer from this region," Vidyasagar said. 73 percent of the Vietnamese population uses mobile phones, according to a report by Vietnamese digital advertising firm Adsota earlier this year.