Invisalign is another great option you could choose given your desire for braces not to be visible to other people around you. Amongst other distinct advantages that it evidently offers, the lisp would be very transient (initial few days) using Invisalign.
Next Steps
Consult a Certified Invisalign Provider (Orthodontist).
Health Tips
It's always good to opt for advanced treatment modalities now that they're readily available at reasonable prices in India. Good luck!