Tanglin Mall has this cute hobby shop on the top floor called Quilts & Calicoes. It caters to the expat crowd so it carries loads of Japanese fabrics, custom design Batik and even Asian-inspired quilt kits. If you love Japanese washi paper as much as I do, you will love this selection. Buy online via their website if you don't want to make a trip down to Tanglin Mall. You will definitely not leave without getting something.
Look around on the same floor and you will find other hobby craft shops selling an assortment of materials.