Some of my doubts are answered when I got the chance upon a Rufous Woodpecker (Celeus brachyurus).
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Perhaps video recording will help...
This is a Crested Myna (Acridotheres cristatellus). One glance it look just like a Javan myna but if you look carefully, it have a different bill shape & colour. The Crested Myna also have a black with white undertail-coverts.
This is a Javan Myna (Acridotheres javanicus) taken in Singapore Botanic Garden. Javan myna have a clean white undertail-coverts.
I place them side by side, can you tell the difference now?