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.
This is one of the most common birds in gardens, cultivated and urban areas in Thailand.

1st photo: Tub Kaek Beach area, Krabi, Thailand, 3 February 2013
2nd photo: Klong Muang beach area, Krabi, Thailand, 20 January 2013
3rd photo: Koh Samet, Thailand, 17 December 2009