It looks like a Syke's / Booted Warbler to me, and I would said I have a preference for Syke's Warbler, because of the overall structure and upperpart color, but more pictures and opinion from other would be welcome to confirm it.
They are usually more easy to separate when seing them rather than on picture.
It is in both case a very good bird for the region, as far as I know a first for Macau, and the Avifauna of Hong Kong mentions two sighting of Syke's in HK. Very good find.
All the best,
Jonathan