In one online source, I read this about the nandivarman pallavan ...
In A.D 731, the Pallava king Parameswaravarman died without any heir and hence the Pallava empire was kingless. Parameswaravarman, was the last ruler of Simhavishnu line of Pallavas. That the enemies may not utilize the opportunity to invade the country, the military leaders (dandanayakas), scholars and representatives of mercantile and peasantry formed an entourage and undertook "a long journey" to reach the kingdom of kambujadesa( modern day Cambodia and Vietnam) ruled by a certain kadavesa hari varma who stemmed from the pallava lineage and was 6th descendant of Bhimavarman, the brother of the great simha vishnu. The king had four sons.The first three declined the offer(Kshatriyamalla, Sangramamalla and Rajamalla). The last one by name pallava malla parameswara also known as Nandi varman, who was then 12 years old accepted the request. Nandivarman's becoming a king at such a tender age is referred to in many inscriptions and contemporary literature(referring to him as "The one of strong arms who got the kingdom at a tender age" or the one who became king at a tender age). "
What happened to the pallavas in the combodia & vietnam after this ? any records abt them ?