Asia Sentinel publishes an article written by Pham Doan Trang about the situation of journalists in Vietnam:

The press card system is a sophisticated method of controlling reporters. No card, no access. Without a press card, reporters can't hope to meet high-ranking officials, visit contacts at public offices or cover official conferences.

The State doesn't need to kill journalists to control the media because by and large, Vietnam's press card-carrying journalists are not allowed to do work that is worth being killed for