I live in one of the Southeast Asian countries, Indonesia
Unlike in Thailand / Sri Lanka, Indonesian people are majority Moslems (over 200 million of the population).
Buddhists in Indonesia are mostly Chinese
& some indigenous groups of Indonesia (depend on location, e.g. in Borobudur Temple area ) Actually there are many Chinese-Indonesian people who confessed themselves as Buddhists (not theradava nor mahayana), but actually they don't really understand about The Buddha's teachings and still equate Buddha with God. Mostly pray with joss sticks and ask for wealth and health, and burn joss sticks as offerings to the devas. Even my Theravadin dad also burn joss sticks in altar, but he did that to respect the devas in my house. I do burn joss sticks occasionally, such as in Chinese new year, pray to my mom & my grandparents, wishing their happiness. In some chinese temple, people burn some giant candles and burn many many joss sticks. Really can't bear with the smoke! I think it's a part of the culture. Don't know if my answer really answering the question
but about Indonesian Theravada, I don't think there's any significant unique things. CMIIW