I gather from your question that your child feels hungry, but has small quantities at a time. Although his weight is less, but height is normal. You have not mentioned whether these food habits have been there since an early age or have been recent onset.    Recent onset may be subsequent to an illness and would recover on its own. If since early age, then also you don't need to worry as child is growing fine despite eating what you think is not enough for him. You cannot force feed a child  at this age. Ensure that healthy, home made food is available at home which he can eat as and when he is hungry. Avoid keeping junk and unhealthy foods at home like wafers, namkeen, biscuits etc, so that child doesn't keep munching on them with no appetite for food at meal times Keep monitoring his growth every six months. If height and weight keep showing increments, don't worry at all

Consult physically

Consult physically

Hello ! Weight is low . Give more of fruits and vegetables. Give apple puree daily . Green leafy vegetables, kichidi with dal carrot beans. Milk daily 2 times

Take small steps at a time. Put a vegetable in the plate. Next time make him touch it. 3rd time make him lick it. 4th time around, make him a eat a piece. 5th time give small portion. This may take weeks but a good & steady progress.