Stir-fried rice noodles were introduced to Thailand from China.
Chinese influence is central to the story of Thai noodle cuisine. Rice noodles and noodle-making traditions arrived in Thailand through Chinese communities and trade, and stir-frying became part of the country’s evolving food culture. The Thai term kuai tiao is itself connected to a Teochew Chinese word for a type of rice noodle.
That history does not mean Pad Thai is simply a Chinese dish. Wikipedia distinguishes between the older arrival of stir-fried rice noodles and the later creation of Pad Thai as a specifically Thai dish. The recognizable national dish emerged in Thailand during the mid-20th century, combining noodles with local sweet, sour, salty, and savory flavors.
Another common mistake is assuming that Pad Thai dates unchanged from ancient Thailand. Its ingredients and technique reflect long regional exchange, but the named dish is comparatively modern. Chinese culinary influence also appears in other Thai noodle dishes, including pad see ew, whose stir-frying tradition is likewise traced to China.