Yes most probably through trade. Check the provided video link on the ancient Pompeii, based on the archeological evidences they had trading activities with other Asian countries including India. It is already known that the Chams already settled in Vietnam during Pompeii time. Their ports popularity at the time probably similar to Singapore today and Singapore is currently the busiest port in the world. Another fun fact is that the Chams ancient capital city is called Simhapura or Lion City, and Singapore original name is Singapura. My gut feeling is that Champa was either playing the role of Singapore today or conquered Singapore, at the time of Pompeii.