Just I have found this in comment on siddha forum .
We now have it: 3 Hindu/Indianised civilisations in Malaya - Kadaram in Northern Malaya, Gangga Nagaram in Central Malaya and now Kota Gelanggi in South Malaya bordering Singapore.
It is clear that the Chola Empire were invaders, colonisers and imperialists, and that Rajaraja was an emperor.
When Tamil histrorians talk about King Raja Rajendra Chola's exploits in South East Asia, we hear only the name of Kadaram that goes by the modern name of Kedah, a state in Malaysia today. Kedah has a wealth of ancient temple structures in the world famous Bujang Valley. Apart from Kadaram, there was also the Kingdom of Gangga Nagaram that lies in ruins today further down south after destruction by King Raja Rajendra.
There is yet another forgotten thousand year old city of Kota Gelanggi, raided by the same King, far down South, in the state of Johor. Its ruins in thick jungle have been established via aerial photos and a ground level expedition is being planned.
The discovery of this place hit the headlines of today's The Star newspaper, the major English in Malaysia.
This is the single most exciting news on the ancient history of Malaysia apart from the Bujang Valley.
That makes me wonder, what was King Raja Rajendra Cholan up to in Malaya? Kadaram lies at the northern extremity, Gangga Nagaram lies a little south of Kadaram, whereas Kota Gelanggi lies in the southern extremity of Malaya. All these were destroyed by King Raja Rajendra Cholan. That seems to me the total destruction of the then existing Malay Kingdoms. This was no ordinary battle but all out war. But why?