Zitting Cisticola

A lanky warbler-like bird of grasslands. Upperparts Buffy-brown. Underparts mostly clean white, with flanks washed brown. Crown chestnut with pale streaking, contrasting with whitish face and brow. Back boldly streaked back. Superficially similar to Pallas's Grasshopper Warbler but paler, and very different habits.

 

Reference:  Birds of Singapore by Yong Ding Li and Lim Kim Chuah