We used a voucher here - these things are very hit and miss as some places get upset if you use them. Not sure why you would utilise the system but at least the staff at Siam were very gracious and we received excellent service - deserved the tip! We had the mixed entree - hot, crunchy deep fried samples, and the fish on lettuce (No9?) this one was great, really tasty. The Green Chicken Curry was too hot for my husband but not enough for me - but very nice and plenty of it. Also had the seafood curry and that was also excellent. Worth a visit.