According to Section 10.1 of the South African police services directive 1/1/4/1 signed by KJ Sitole the National Commissioner of the South African Police services on 22 January 2019 the following applies –
10.1 Passengers flying on a commercial airliner with small amounts of cannabis:

Provided that the quantity of cannabis is small and based on all the circumstances of a specific matter, including the concealment of the cannabis in a bag or luggage of a passenger, possession for personal consumption, by an adult passenger on a domestic flight is permitted.
Is it safer to travel with weed on a plane in your hand luggage or suitcase? We think hand luggage is better because then you are present if it gets questioned. To survive the questions, you need to know your rights and quote the police directive above!