You say that you're looking to lose fat, but not looking to thin or lose weight. Those are largely contradictory goals. You might be able to lose fat while maintaining weight, but that means gaining the same weight back in muscle, which will never happen if you're just doing arm and chest exercises, because you're working on such a limited subset of your muscles that even if they experience large gains, those gains will still be small compared to the total size of your body and the amount of fat you have.
So you're 67kg. Let's make up some numbers and say that you're 25% body fat. This means that you have about 17kg of fat in your body. If you were to cut down to 10% body fat without gaining any muscle, you'd need to lose about 11kg of fat.
Now let's consider how much muscle you could realistically gain. You're only working your chest, arms, and presumably shoulders. Those are not particularly big muscles, and in total, for you, probably only weigh about 2-3kg. Let's say you have a hugely successful training program which doubles the size of all these muscles. You're just gained 2-3kg of muscle, which doesn't even come close to the 11kg of fat that you were trying to lose. In fact, the size of these muscles would need to increase four-fold to compensate for the weight reduction due to fat loss. That's not going to happen.
So, here's what I would suggest: Firstly, get a better training program. A whole body training program, which includes back and leg exercises like chin-ups, deadlifts, squats and leg press. This will actually work the larger muscles in your body and allow you to put on amounts of muscle mass which aren't insignificant. Secondly, the main measurements you should be paying attention to are progress in the gym (i.e. how much weight you can lift in each exercise), and your waist circumference. If your bodyweight is staying the same but your waist circumference is going down and your strength is going up, then you're losing fat and gaining muscle. If your waist circumference is going up, then you're gaining fat, probably an indication that you're over-eating. If your strength isn't going up, that's most likely a sign that your training is inadequate, or you're not eating enough.