Malaysia consists of 3 races: Malay, chinese and Indian. Therefore, you must know at least one of the three main languages in Malaysia, Mandarin (Chinese), Tamil or Malay. Or else you couldn't live here just talking languages that some don't understand.
If you are intending to stay in Malaysia for the next decade, in this situation you MUST learn Malay. Why? because you're in Malaysia! If you don't, you wouldn't even be able to communicate with Malays and that will cause a headache to you when you need to apply something or what (applcation forms are mostly in Malay). So, the #1 thing to be a Malaysian is to learn Malay (then Chinese and Indian).