In the picture below, the two larger black ants were Black Valentine Ant (Crematogaster laeviceps). When I saw this ant in the field, I thought it was the Asian Army Ant (Pheidologeton diversus) as it was small ant thus making it difficult to differentiate between the two. Also, the formation of the marching column looked similar to the Asian Army Ant. The only thing that puzzle me was the lesser aggressiveness of it when compared to the Asian Army Ant. When I examined the picture back home with a magnified view, it turned out to be another ant species --- no wonder it was not aggressive.
It might also look similar to the Cocoa Black Ant (Dolichoderus thoracicus). However, the Cocao Black Ant is larger in size and only slightly smaller than the Black Valentine Ant.