This Linderia crustacea or with a common name Malaysian false pimpernel according to wikipedia is a kind of flowery weed that is commonly found around the garden.
I was a bit surprised to know that this weed is kinda a new species from this Genus. Maybe they come from different parents that travel across the globe and end up in South East Asia. : )
If you look around your yard, you might notice some of this weed in your garden. I even found this species in the garden of my workplace which is always maintained and cleaned by one of the gardeners, and still, I can find one thriving in the garden.
What is interesting about this flowering weed is that the top petal will always cover the center of the flower. While most of the flowers will open up to the fullest when they bloom, this one is a bit different. I can't find the answer yet, if you know why, please don't hesitate to let me know. :)