Lesser green leafbird (Chloropsis cyanopogon cyanopogon)

Subspecies found in the southern Thai-Malay Peninsula, Singapore, Riau Archipelago, Sumatra, Nias, Bangka, and Borneo.

Male birds can be clearly differentiated with the greater green leafbird (C. sonnerati) by their more smoother bill (Unlike the upper bill that face downward seen in sonnerati) and with the black plumage on their throat only extending equal to the eye (Unlike sonnerati which extend above their eyes).

After looking into it a bit more, this bird is very likely an Sumatran leafbird (Chloropsis media)! Notice the yellow colored forehead.