Answer:
Beginning around 800 CE, the mainland of Southeast Asia was mostly Buddhist. By the 1400s, Hinduism had spread across most of the islands in Southeast Asia.
Explanation:
The first answer is Buddhist.
The Buddhism really grew during the first millenium of the Common Era.
However, during the Medieval period, the Hinduism started to take control and became the most popular religion in Southeast Asia. So the second answer is Hinduism
