We're going to need some better pictures. My first inclination is that this is a small Heosemys grandis. It's really hard to ID for sure with the badly eroded shell missing so many identifying scutes. A top picture to see how serrated the rear margin of the carapace would be helpful. It seems to be very serrated which leads me to the Heosemys. The top jaw is also bicuspid. What I do see of plastral pattern leads me to H grandis as well. A good picture of the full plastron would be very helpful and a good head and neck shot would help.
@Aequor the Malaysian Giant Turtle - Orlitia borneensis does not have a serrated rear margin and does not have the bicuspid jaw.
Hi there, yes its a turtle, its called Black Marsh Turtle, you can find basic information in here: https://en.wikipedia.org/wiki/Black_marsh_turtle
The specific identification is it has white colour on its cheek.
Correct, black marsh turtle (Siebenrockiella crassicollis). They can be very personable, but also very finicky eaters. Even young ones that are raised to adulthood run into feeding issues. Best bet is to turn it loose, unless you can provide their very narrow diet......
Agree completely with @harris and @cputra19 It is indeed a "smiling turtle" - the Black Marsh Turtle Siebenrockiella crassicollis. The head shot you posted later helped confirm and that distinctive triangular nuchal.