Female Fighting Spider (Thiania bhamoensis), Mount Faber, Singapore
A type of jumping spider.
From Wiki: "Because two males will readily fight each other, either in a natural setting, or if put together, they are commonly known as "fighting spider" in South-east Asia. These spiders are commonly kept in matchboxes with a piece of green leaf and a spat of saliva for moisture. A spider that wins fight after fight gets the status of "first king". A common belief is that the darkest males are most aggressive."