The Oriental Magpie Robin (Copsychus saularis) is an excellent songster that is often detected by its melodious song. 
Males have distinctive black upperparts and white underparts, while in females their upperparts are grey instead.

1st & 2nd photo: Singapore Botanic Gardens, Singapore, 7 November 2022
3rd & 4th photo: Sungei Buloh Wetland Reserve, Singapore, 25 October 2022