Hi,
I bought my fabric for my cheongsam from Arab Street (Royal Fabrics) and they recommended me a seamstress at Tanjong Katong Complex called Irene. Sorry can't rem the name of the shop, but it's got the word IRENE as part of the shop's name. It's either on the 3rd or 4th flr. If I find the namecard, I'll post the details here again. The fabric from Arab St (lace with flowers sewn on & tulle for the lining) cost me $180. The cost of tailoring the cheongsam was $90. The seamstress (Irene) took my fittings only once and when I saw her 1 mth later to pick up the cheongsam, it fit perfectly so no need for any alterations.