Deng-- I agree with lemonman. Try weightlifting. Weight lifting is specifically designed to work your muscles and allow weight gain. It is also specifically designed to make you strong, if you are willing to do it for a long time.
If you enjoy sports such as swimming, cricket, football, or anything else, then by all means play them.
Gaining weight is about eating enough to grow. It will not matter what sport you play or how much you lift weights if you do not eat enough to grow larger every day. Not just a couple days of the week, or a couple weeks out of the month, but EVERY DAY.
The sports you play or the weight you lift will decide whether the extra weight is muscle or stomach fat. Eating more will make you grow.
Look at my response to you above--those rules will help you grow if you apply them and also lift weights consistently 4 times a week. Write down what you eat, the times you eat, and how much protein and calories your food has. Use a notebook or a website like dailyplate.com to record it. Lift weights 4 times a week. Then weigh yourself once a week to see if you are gaining weight.
If you are gaining weight, good. If you are not, look at the calories you were eating that week, then add 300 calories to those numbers and eat that amount every day while lifting weights.