When Facebook and Google want to strike ad deals in Vietnam, salespeople in Singapore get on a plane and fly to major cities like Ho Chi Minh City. They rent out rooms in five-star hotels for meetings with small retailers looking to sell around the world or big brands wanting to reach Vietnamese consumers. Vietnam is the most important market in Southeast Asia for both Google and Facebook, but neither company has any full-time employees stationed there.

That’s because Vietnam is governed by an authoritarian communist regime that imposes strict censorship of online content such as social-media posts and user-generated videos critical of the government. While Facebook and Google comply with the government’s requests for removing or restricting content, people stationed in the country would be vulnerable to pressure for information about the identity of users posting content, said people familiar with both businesses. According to these people, the companies worry that staffers could be arrested or the offices raided, and even route advertising fees through subsidiaries in Ireland and Singapore to avoid Vietnam’s banking system.