Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Surabaya to Johannesburg OR Tambo Airport as you normally would.
Surabaya Juanda (SUB) is the airport you will fly out of if you book a flight from Surabaya to Johannesburg OR Tambo. You should not have trouble finding flights to Johannesburg OR Tambo from Juanda; the airport handles an average of 0 outbound flights to Johannesburg OR Tambo per day. You should also have plenty of airline options to choose from since 0 airlines have flights from the Surabaya airport to Johannesburg OR Tambo. It is only a 15.0 km journey to Juanda (SUB) from Surabaya’s city centre.
This is defined as Surabaya Juanda Airport (SUB) and Johannesburg OR Tambo Airport (JNB). Codes like Johannesburg OR Tambo Airport are often used to just call airports uniquely.