Do I need to book my Ward in advance for delivery in KKH ?

Hello ! I am wondering, if I have decided I what type of ward I would like to stay during my delivery in KKH, do I need to let my doctor know in advance ? Or I can only get to choose right before I get admitted into KKH on my actual delivery day? I know I might sound a bit Kiasu , but I really want to ensure that I could stay in ward A (single bedded) , so that my Husband can accompany me with a sofa bed for him. Thank you !