Only 20 countries maintain formal relations with Taiwan, a list that has shrunk by two since Ms. Tsai took office in May 2016. She has resisted demands from Beijing that she endorse the so-called One China principle, which holds that Taiwan and China are part of a single country, although each side has its own views on how that country is defined.

In December, Mr. Trump briefly cast doubt on America’s adherence to its One China policy, when he broke with longstanding practice by sharing a call with Ms. Tsai. He later said he would honor the policy, but his Twitter message announcing the conversation stunned China watchers and gave Ms. Tsai her first taste of global exposure on social media.

Weeks later, Ms. Tsai stopped by Twitter headquarters in San Francisco, on her way back from visiting diplomatic allies in Central America. The company had contacted Ms. Tsai’s office about reviving her account, said Vincent Chao, chief of staff to the secretary general at the Presidential Office.

Ms. Tsai, who joined Twitter in 2010, had previously posted in Chinese, but she stopped in May 2014, primarily because relatively few people in Taiwan use the service, Mr. Chao said. For domestic engagement, Ms. Tsai posts in Chinese on her Facebook page, which has more than 2.1 million followers.

Describing the past few months of Twitter diplomacy as “fairly successful,” Mr. Chao said that the number of people who follow the account had risen since January from 36,800 to more than 100,000. They include foreign journalists and others who can communicate Taiwan’s positions.

“It’s followed by journalists from most major publications from around the world,” he said. “Increasingly, we’re seeing interest from politicians in the U.S., Japan and other democracies.”

Alex Huang, a spokesman for the Presidential Office, noted, “The broad role of this is to increase international exposure for the president and Taiwan.”