If, as is currently believed, Vietnamese is an inbred sub-population of Edwards', then this is an Edwards' as well as being a Vietnamese. Either way, it Is possibly extinct in the wild, and we need to ensure its future in captivity until restocking the wild becomes feasible.
If this is the bird I think it is (shares an aviary with Wrinkled Hornbill 'Homer', and a single Bali Starling), he will display to a green watering can with a washing up brush pushed down the spout, which must look sufficiently like a rival Edwards' cock..