thank you Grahame for this inputs and your ID of this bird as the common Paddyfield Pipit that we see often on the open field here.
I have taken many pictures of the Paddyfield Pipit and none have the clear submoustachial strip.
btw, Richard's Pipit was being spotted in Singapore in 19 Oct 2015, as per
Richard’s Pipit – Singapore Bird Group.
looks like I have to go back and get more pictures of this bird before it move on.