For my 7 yrs boy, sticky dry hair falling found on crown of head getting bald past 5 months and it extends its area mostly downwards back of head, it is by hair problem or any internal and who to seek medical help ?

Alopecia vs fungus: Child probably is developing alopecia. It would be important also to rule out a fungal infection of the scalp. Best would be to see a dermatologist who can do a Woods light examination and a KOH prep and tell you the diagnosis and treatment right away. If it is Alopecia he will also be able to guide you properly and reassure you. If required further work up can also be initiated.