NAL, but have made payments from India to entities in other countries.
Your client should be making a bank transfer. They are to approach their bank’s foreign exchange branch. They will have to fill out a couple of forms on the nature of the transaction, attach proofs such as invoice, purchase order, etc. They will also have to sign a couple of declarations and waivers. The bank will assist with the process.
This is assuming that this is a business transaction and not a personal one.