Hi, just read your message (I don't visit this site very often) and I hope my reply is not too late...
I am Malaysian who used to live in HK and had account at HSBC HK. We can use HSBC credit card to withdraw money from most of the bank ATM machines that accept Visa, but cannot withdraw money using normal ATM card from any bank in Malaysia, including HSBC Malaysia.
Further, there are not many HSBC bank in Malaysia. In KL, I only seen one HSBC bank. I am not sure about Kuching.
My advise is to exchange as many ringgit as possible and use credit card to withdraw cash from local banks in Malaysia.