You can use coconut oil for hair. Best way to use is, apply coconut oil 1 hour before bath, and then wash with shampoo. Dry hair in good sunlight. But it doesn't decrease thinning, it doesn't increase density.
It just gives a look of shiny hair.
Next Steps
consult Dermatologist online/physical for prescription to treat thinning of hair.
Health Tips
Don't rub while drying hair after taking bath. just press with towel and dry the hair in sunlight. Don't apply unnecessary oils marketed outside. no evidence yet to prove their efficacy.