I am considered skinny last time, but I've been putting up weight the current past few weeks.
Solution, eat few times daily instead of the daily meals. As maybe we have high metabolism, the only way is to eat regularly. As in small portion of your lunch you distribute it to 2 times then dinner also 2 times, breakfast. Or rather follow the 4 hours 1 meal.

Go to gym to help build lean mass muscle. That's what I am doing.

Why dont the people who wanna loose weight tell u how to gain weight ,and u tell them how u are so slim...haha... this world is so unfair  ..

U are those body type that will find putting weight difficult as well as putting muscle difficult. But that does'nt mean u can't try. Like the other said, eat a lot ( make sure eat supper ) and hit the gym....it will help.  Anyway, the next time u feel sad that u are thin...... just be glad at least u are not overweight.

Take 3 normal meals a day. After each meal, drink shake (from herbalife). You will gain your weight. The shake has vitamins needed by our body. You need to nourish your cells in order for your cells to be healthy. Do you know our body is made of cells? Other than that, you also needs protein, soy protein or whey protein. Herbalife products able to help you. You may give it a try.