In 1918, they joined eight other Thai students travelling to Boston, Massachusetts. As the train drew into Boston station on 21 September 1918, Prince Mahidol was waiting to welcome them, though Sangwan had no idea who he was. Furthermore, she had no idea that her presence had already made an impact on the young prince, who, according to his roommate, Pradit Sukhum (later Lord (Luang) Sukhum Nayapradit), arrived home after two in the morning, shook him awake saying, "The two girls have arrived. Sangwan is really very pretty, you know."