There were other deities like Ganesha in Thailand, which were clearly of Hindu origin. Of course, Buddhism was itself an artificially separated religion; its concepts flew seamlessly from the earlier streams of thought enshrined in the Vedas.
But the biggest Indic influence I saw was in the diffusion of Sanskrit into the languages of the region. Bahasa, bumiputera, samudra, rasa, jaya and raja were just a few of many Malay words that were rooted in Sanskrit.
And yet , to my surprise, the museums I visited in Malaysia were more focused on European colonial powers, which became significant only during the last 400 years.