Here's a page from South African Customs that may be useful: Arrival in SA
As a practical matter, no. Personal effects that travelers bring in with the intent of bringing them back out at the end of a visit are generally exempt from duty, and South Africa appears to be no different in that regard. You are allowed to bring "personal effects" (except for prohibited and restricted items, like illegal drugs or weapons) without payment of duty, as long as you'll be taking them back out of the country with you. This is why your clothes aren't subject to duty either. You can also bring 5,000 Rand of goods duty free, such as gifts you plan to leave in South Africa.
You can see this on the Traveler Card you'll be asked to complete as well:
Personal effects and/or sporting and recreational equipment are duty and tax free if brought in by:
- Visitors for own use and if goods do not remain in South Africa
Now, for some valuable items, it's possible that they'll want a deposit, to make sure that you don't plan to leave the goods behind and evade payment:
Please note that you may be required to lodge a cash deposit to cover
the potential duty/tax on expensive articles if you are bringing them
in on a temporary basis. The deposit will be refunded when you leave
after a Customs officer has physically inspected the items and
verified that the goods are being re-exported. Visitors must notify
the Customs office where the deposit was lodged at least two days
before you leave to ensure that the refund is ready. You will find the
office number on the documents which will be given to you when paying
your deposit.
If you are leaving from a port other than the port where
you lodged the deposit, the inspection report confirming the
re-exportation of the items will be forwarded to the office where the
deposit was lodged and a cheque will be posted to the address that you
provided.
A deposit requirement like this for an ordinary business traveler's laptop seems quite unlikely to me. Travelers routinely bring their used laptops and other common electronic items with them to many countries without incident or charge. In the very unlikely case that Customs believes you plan to leave the laptop in the country, they have the right to require a deposit, which you can reclaim on your way out after you present the laptop.
It would be a good idea to have some kind of proof that you bought the laptop in India and paid taxes on it there, so you can demonstrate to Indian Customs officials that you are bringing it back and should not be charged duty on it.
