Vietnam received 1.6 million Chinese visitors against Thailand's 1.3 million, according to data from their tourism ministries.
Last year the number of Chinese arrivals in Vietnam had only been around half of Thailand's.
Thailand received 24% fewer Chinese visitors year-on-year, and the government is now considering adjusting its targets to reflect the current situation, Nation Thailand reported.
In recent months concerns over tourist safety have grown in Thailand, particularly after the kidnapping of Chinese actor Xing Xing in January.
The country targets eight million Chinese visitors this year, but industry insiders have warned it may fall short of this goal also due to rising competition from destinations like Japan and Vietnam.