Hi
Artisan D'Ankor is the best upmarket shopping in Siem Reap. We stayed at the FCC Hotel there which was great and ALSO had the BEST shopping arcades on its premises. (gorgeous silk clothes and bedding at Jasmine there.) There is a market along the riverside which sells everything from fresh food to well, everything else. I got great silk handbags. Woven handbags. Silk scarves.
Along the roads AROUND the market square is most of the other shopping, including the charity shops.