Grahame is correct, it's a female Malaysian. Note that the orange throat is quite pale, and also extent of orange on the underparts - doesn't extend further than the breast.
In addition, note that orange reaches bill base (certain species there is a blue chin, ie Large-billed).
Mangrove is at Danum Valley - we photographed a roosting bird there last year, despite never seeing, or hearing, it there previously. It is really a coastal forest and oil palm edge species though.
James