I wouldn't normally question you Grahame, but this bird was definitely not Grey Bushchat. I coincidentally saw a pair of Grey Bushchats this afternoon, my first encounter with the species, and the bird in the picture was very different. For a start, the mantle was darkish chestnut. I have also ruled out Black-headed Sibia as the form found in Dalat is robinsoni, which is completely different to Dark-backed Sibia. I now think this bird must be a White-cheeked Laughingthrush.