In southern Sumatra (modern-day Indonesia) a Malay city-state, Sriwijaia (perhaps identified with Palembang), controlled a cluster of dependent city-states during the period roughly 650 A.D. until 1050 A.D.
In Sumatra/Malaysia a number of Islamic city-states can properly be identified (Melaka, Aceh, and Brunei, among others) between 1450 A.D. to 1625 A.D.
A number of Thai city-states could be identified between 800 A.D. and 1700 A.D.