Vietnam was called Nagar Champa from the 1st to the 16th centuries.
The Cham people of Indonesia occupied the central & southern coast of Vietnam from Neolithic times & established the kingdom of Champa. Their capital from 7th to the 9th century was Indrapura/ Tra Kieu.
That Hindu Kingdom of Champa, is now called Vietnam.
Temple inscriptions from Champa indicate that Ramayan was known there by the 7th century CE.
Ram and Krishn are found in the temples that are predominantly dedicated to Uma Maheshwara.
Evidences:
Many ancient inscriptions found in Khmer monuments by numerous rulers were written in Sanskrit or Old Cham & have been found throughout Central Vietnam.
During king Isanvarma and Prakasadharman, an inscription gives tribute to Rishi Valmiki.
Khmer Kings were called Kurung Bnam/ (mountain), meaning Shilaraja, which explains the Sacred Holy mountain that connected them to ancient India.
Source/Credits: Meenakshi Sharan, Ayodhya Foundation, Global Ramayana Connect on Facebook