Trade tension may be taking a toll on Chinese tourist arrivals in Thailand, hurting a key engine of growth for Southeast Asia’s second-largest economy.

Chinese arrivals slumped 11.8% in August from a year earlier, the most since February 2017, according to Bloomberg calculations using government data released Thursday. The Tourism Council of Thailand said concern about the economic fallout of the U.S.-China trade war, as well as the strength of the baht, may be putting some travelers off.

Tourism accounts for about a fifth of Thailand’s gross domestic product. Chinese travelers are expected to contribute close to a third of a forecast 2.09 trillion baht ( billion) in foreign tourism revenue this year, according to ministry figures.