The Khamer Empire existance is recorded since 800CE and spread throughout South Asia. Its remains fell to Thailand and today Angkor, the capital of Khamer Empire is evident through inscriptions and buildings like Angkor Wat.
Ref: http://webecoist.momtastic.com/2011/05/02/lost-civilizations-12-societies-that-vanished-in-mystery/
Up north of Malaysia in Merbok, Kedah is Bujang Valley. Artefacts and buildings are recorded to be 110AD. This makes it older than the Majapahit kingdom 1200AD and significantly means some form of civilisation and trading was already in place.
Ref: http://anilnetto.com/society/malaysian-history/bujang-valley-earliest-civilisation-in-s-e-asia/
Down south of Malaysia is a city from Srivijaya empire, known as Kota Gelanggi. Its exact location is not know but is said to be along Sungai Lenggiu, Johor. Based on writings, its said to exist around 600AD.
Ref: https://en.m.wikipedia.org/wiki/Kota_Gelanggi
https://plus.google.com/114394192029978256918/posts/N7wR5AHPSyd
Does these sites have connection to the Khamer Empire?