A huge swath of Indonesia is also malay. That is why indonesian government is very sensitive to the usage of bahasa melayu but decided to use the term bahasa Indonesia.
And when dr m told sultan of johore to reclaim land lost to english and dutch redelineation which split johore riau empire in two instead of making a fuss about pulau batu putih ( pedra branca), indonesia was very quick to defend its position as sole authority on it.
Those malay territories in indonesia speak malay like sinkie or jiu hu malays. And wear same traditional attire and similar custom. A huge swath of sumatra, kalimantan, kepri ( kepulauan riau, consist of islands such as batam, bintan, atuna, anambas....) are just like peninsular malays and they could make or break indonesia.