Vietnamese political blogger Nguyen Huu Vinh (L) and his assistant Nguyen Thi Minh Thuy stand at the dock during their trial in Hanoi on March 23. (Handout/Reuters/Doan Tan/Vietnam News Agency)

THIS MONTH, President Obama is planning to visit Vietnam for the first time, the third presidential visit since the end of the war more than four decades ago. While the interests of the United States and Vietnam are growing closer in trade and security, Mr. Obama must pay attention to Vietnam’s dismal record on human rights. Although Vietnam has enjoyed rapid economic growth in recent years, it remains a one-party state that denies freedom to its people and rules by force.

The closer economic and security relationship with the United States has a sound logic. Vietnam has joined the proposed Trans-Pacific Partnership, which the Congressional Research Service recently called “perhaps the most ambitious [free-trade agreement] undertaken by the United States,” an important anchor of the U.S. pivot toward Asia. Vietnam is also at the front line of tension over China’s grab for maritime power in the South China Sea at the expense of its neighbors. Vietnam is eager to buy more high-tech weaponry from the United States. Mr. Obama is considering whether to lift the remaining ban on arms sales, partially relaxed two years ago to allow maritime purchases.

The lifting of the arms ban appears reasonable, but Mr. Obama should insist on real improvements on human rights before proceeding. What Mr. Obama says really matters, and Vietnamese leaders cannot get a free pass. The ruling Communist Party holds a monopoly on power and restricts basic rights such as freedoms of speech, opinion, press, association and religion, often through physical intimidation and harassment. The nation’s penal code also criminalizes the exercise of many basic rights.

We’ve called attention recently to the lengthy prison terms delivered to bloggers, lawyers and activists for speaking out, but these are not the only victims of the regime’s intolerance. A sizable and diverse group of independent candidates attempted to run for the National Assembly recently to test whether candidates who were genuinely not party members could get on the ballot in a complex, multi-stage process that begins at the equivalent of the neighborhood or precinct level. Among those making a bid was a popular singer-songwriter, Mai Khoi, who, while not a dissident, told a reporter she was seeking more openness in politics. She was shut out, as were almost all of the independents. Mr. Obama should meet with Ms. Khoi and press Vietnam to release Thich Quang Do, the leader of the Unified Buddhist Church of Vietnam, who for three decades has been in prison, in internal exile or on house arrest. He has written a letter to Mr. Obama, asking him on his visit to “speak out for the thousands of Vietnamese” being punished for seeking religious freedom, democracy and human rights. Mr. Obama must not neglect to do so.