The options are quite limited, they will be:

1. Some over the counter or prescription medicated drug.
2. PRP (Platelet rich plasma therapy) for hair, wherein blood will be extracted from the site where healthy hair growth is observed, some cells will be extracted from it, and then the platelet rich plasma that is obtained will be injected into the site where hair thinning is seen.
   PRP treatment cost will be anywhere between Rs. 4,500 to Rs. 20,000.
   Our blog will explain more about eligibility, step-by step process and prp injection recovery time - PRP Hair Treatment.
3. Or it will be hair transplant surgery as a final resort.
   Hair transplant price will be 25-45 Rs. per graft, each containing one to 3 follicles, and number of grafts will be determined by dermatologist.
   More details regarding procedure, techniques, price variation and hair transplant side effects are available here - Cost of Hair Transplant in India.
4. Some clinicians could even use Lower Laser therapy, but studies are conflicted about same.

You should visit dermatologists regarding same - Dermatologists in India.