As quoted from Wikipedia:
Historically, before the arrival and spread of Islam in the 15th century, and the spread of Christianity from the 19th century, the inhabitants in the land were either Hindus or practiced indigenous faiths.
In the peninsula, widespread Islamification is said to have begun in 1409 after Parameswara became Sultan of Malacca and converted into Islam after marrying a princess from Pasai. Since then, other Sultanates in the Malay peninsula have adopted Islam.
Similarly in East Malaysia, folk religion was widespread prior to the arrival of Christian missionaries from Europe. The practice of headhunting was quite common in these societies. In Sabah, the Kadazan-dusuns would worship Kinoingan or rice spirit and celebrate Kaamatan or harvest festival every year.
In Sarawak, it has been said that the animism practised by the Ibans (Satsana Phi) and other related groups is the most developed, elaborated, and intellectualised in the world.
Wikipedia (2016) . Malaysian folk religion. Available from < https://en.wikipedia.org/wiki/Malaysian_folk_religion > [24 Feb 2016]