all you need to do is just bring yourself and your IC to RHB bank and let them know that you want to activate your account.

only thing that you need to scared of is that they have deactivate and the balance of the money in there is not retrievable. This is valid under law of Banking in Malaysia that once your account has been idle for certain period of time. Before they do so, they will normally send a letter to your mailing address when you registered the account to notify u that.

bring your ATM card just in case.

Thanks.
IC will do actually. ATM card is just an extra. Bank book, you can just let them know that you don't know where it has been. That's normal. Some banks don't even provide bankbook in the beginning. For e.g., last time when I opened my bank account for work purpose, they didn't give me the bank book at all.

Not to disagree your statement fully on this. Just to let you know that the bank has the right to terminate your account and "eat" your money as compensation. (ops, not "eat", take is more appropriate)
Reason i'm saying this is i have a Maybank account and it was unactive for quite some times. They sent me a letter saying that my bank account is going to be deactivated and asking me to activate the account by doing transaction of any amount. Fail to do so will result in terminating the account and the balance in the account is unretrievable. Well, this is for Maybank (one of the shittiest bank in Malaysia due to other poor service )