I only know of Classic Sports (Toa Payoh Safra) have. Other places i not so sure, have to count on other Spore BF'ers info.
Yue Yang Sports Equipment Blk 474 #01-108 Tampines Street 43 Singapore 520474 Tel: 67864818 I was told they are the sole agent for Kason TSF Glory Series.
I think it's run by Zhang Qingsong? Have been to the shop once and was quite disappointed with the limited range of products on display. Was told that most products were out of stock and have to pre-order. Would not go there unless you have something specific to buy or if you're looking for a full Kason package (ie racket/bag/clothing/shoes). Actually you may not find much Kason products in badminton shops as believe these are sold mostly through the Kason coaches. Todate have only seen some Kason rackets on sale at: 1) Classic sports as mentioned by Slacker above 2) Shop at Queensway 2nd floor (run by an Indian boss) 3) Sports shop at City Plaza 2nd floor which carry limited Kason products. You might have better luck in Bangkok if you visit the shops near the Stadium as Kason is quite popular there.
What Sealman said is close to what I understand about the Kason distribution in Singapore - that there is no proper retail outlet here actually selling Kason rackets. The distribution right was owned by a Chinese-national who coaches in Singapore, who donot bring in many stocks because he does not own a shop. Pre-order is preferred. That would explain why there are only limited Kason rackets we see in Singapore. This is very similar to brands like SOTX, that because of it being relatively less popular, the distributor would not want to risk to bring in large volume or large varierty of models. You really need to know what you want through research or words-of-mouth and pre-order from the retailer.