that's alot of options.
hmm...
SA will likely be SAExpress. We did ID95 tkts JNB to Richard's Bay for safari in Kwaa Zulu Natal.
Make sure you have you anti malarial options for Kruger
Keep bags as carryon if possible--high risk at JNB for theft between INT/DOM flights

Thailand--as much as we LOVE going to SA, Thailand is great on the wallet and transport $. Hua Hin is a great beach town 3 hrs/train south of BKK, flts to Chaing Mai are fairly cheap or nt train (see maninseat61.com)
Food is outstanding and accoms are, too. Kanchanaburi (River Kwai is a must do on the way to CM if you take train) Worth a full day--maybe more at river camps.
Also, Amphawa is small floating market town for locals outside BKK. I have guesthouse info for there--right on the riiver, monks paddle up early each morning for offerings and food.
You can work your way up north thru Ayatthura (old capital) too.
I'd be looking at any festival or holiday dates in any places, for sure.
Can't wait to hear your choice as plans progress, too.
One good point, Tony is that you have UA and DL to travel NRT/BKK/NRT