Wikipedia（英文）上明確說李和其妻的母語為英語，1955年前，他不識字！

Lee and his wife, Kwa Geok Choo, were married on 30 September 1950. Lee speaks English as his native tongue and Choo spoke English as her mother tongue. Lee started learning Chinese in 1955 at age 32, before which he was illiterate in Chinese. Lee also learned Japanese as an adult and he worked as a Japanese translator during the Japanese occupation of Singapore.------Wikipedia