What exercises should i do regularly to gain weight in healthy way?

Eat Healthy First!: In order to gain weight your body needs the building blocks to do so, healthy foods provide these in the form of vitamins & nutrients. Meals should have lots of fruit and vegetables (whole not juice) and should have balanced carbs and protein. Those looking to build more muscle might want to increase protein but don't overdo it. Once you are eating healthy any exercise 30-60 min a day will do!

Weight lifting: If you want to gain weight though excercise you need to put on muscle. Making sure you are eating enough healthy food combined with weight training will do that. You should start the weight training program with supervision from a coach or trainer to insure you are doing the correct exercises safely.