Mo has always been slim. But it seems she lost weight since last year. She was super skinny in Tawan Tud Burapa and Sorry I Love You. She looked her normal weight in Club Friday The Series with Toomtam though. Maybe it's just the styling? I really liked her natural makeup in there because it made her look refreshing. Even though it was minimal, it still made her look pretty. Her natural makeup in here, Tawan Tud Burapa and Sorry I Love You makes her look plain and washed out.
There's nothing wrong with being skinny. Many people are naturally slim and it doesn't mean they're unhealthy or starving themselves. That's usually not the case. If you look at Mo's childhood pictures and predebut pictures, you'll see that she's always been skinny. Plus, Mo is 5'2 and has a very small body frame/skeletal structure, so that really makes her look skinnier than she actually is.