It's a 'sun-bird'

 I could have missed it, solitary and quiet, and disappearing as soon as spotted, or so.

The Ashy Minivet (Pericrocotus divaricatus)(Burung-Matahari Kelabu Biasa) is a song bird, alerting its presence with incessant trilling calls, always in a flock, rarely alone.

What's in a name?
It's a grey sun-bird, 'burung-matahari' going by its local name, and once upon a time was also known as Burung Mas Padang, 'field gold-bird'.