I am 33,male,height 5.5 feet, my present weight is 44,slim, I want to become fat and want to raise my weight to 52 kgs.

Well,there are 2 main ways to gain weight.The first is taking in more calories than you actually consume each day.Based on your figures,I'd say you need 1907 calories daily just to maintain your current weight if you are moderately active and about 2161 calories if very active.To gain weight you would need to consume much more than this.Let me just give you a pointer:1 pound of body mass contains approximately 3500 calories which means an extra gain of this calories by the body would give an additional pound of mass, a deficit would mean a pound loss by the body.Now this may not work for everyone because some are naturally lean,It's in their genes, so no matter how much they eat there wouldn't be any significant weight gain.If that's your case then what you are looking for is muscle gain,not to gain fat because it's not going to workout.So start a muscle workout like lifting weights(note:pushups and pullups will not work,trust me).Always do as many reps as possible i.e to your limit every 'ONCE' a week.With time,keep on increasing the weights(This is VERY IMPORTANT).If not,you won't go far.That's it for the exercise part.Now,what is going to make this work is your nutrition during the workout program.Eat 4-5 times a day focusing mainly on protein foods for building your muscle.Your protein intake in grams per day should be 1-2 times your body weight in pounds.Try taking whey protein.It's the best form of protein available.Well,that's it.but this is only if the first option doesn't work out.It is really stressful but it is the only thing left for you to do now.So,if you are really serious,u should give it a try.Trust me,you won't be disappointed.

Just eat and eat and eat! Then u will become fat + There are some pumps u can use to do that! Happy fattening! :D :)