You have to understand that Income tax and GST are 2 separate tax laws.
Regardless of whether GST is payable or not Income Tax has to be paid.
Yes you need to take GST registration for any export of services or goods or both.
In your case since you are providing services to foreign parties, your services are considered as interstate outward supplies in GST. You need to take GST registration.
Also you need to pay GST, for which you can claim refund later.