What is the smallest bird in the hawk family?

It most likely be Black-thighed Falconet (Microhierax fringillarius) in South-East Asia, about 14-16 centimetres (5.5-6.3 in) long and eat smaller birds. Some website also mentioned White-fronted Falconet / Bornean Falconet (Microhierax latifrons) which about the same size.