Apples and oranges?
Because South Korean did NOT have Japanese invasion and occupation, depressions, famine, "Civil War", Chinese invasion, American devastation, or COld War with China?
There are qualitative differences. The actual Korean war lasted only three years. South Korea is the beneficiary of 60 years of peace and security, during which the United States invested heavily in the country and its defense, and provided preferential trade treatment.
South Vietnam was the result of sore losers in trying to frustrate an independence movement by partitioning the country. The 'civil war' was on since day one, and essentially endured through the entire history of South Vietnam. The South Vietnamese government, unlike the South Korean, seems to have been hobbled with institutional and infrastructural corruption since day one.
If you want an Asian comparison to South Vietnam, then your most appropriate standard is probably Afghanistan - another state which has experienced several decades of continuous warfare/civil war/foreign occupation. Not all outcomes are positive, consider Haiti.
If you are going to argue that South Vietnam or Vietnam as a whole might have done better under some other circumstances.... that's extremely vague and its hard to provide a constructive response, except to say 'in OTL Vietnam was so horrifically screwed every which way that almost any POD would lead to better outcomes.'
And they both have SOuth in the name.
Which really is the best thing you've got going for you?
I don't claim to be an expert on post WWII Asia...
But does that excuse your not doing any work at all? It seems to me that if you put an idea out there, or advance a thesis, isn't there an obligation on you to do some kind of homework. To think it through carefully, look at the variables, and then put something more coherent than a random brain fart on the table?
You have a notion "Could South Vietnam have paralleled South Korea's development..." Well... explore that?
So, as I said, IMO, that big WI with South Vietnam is how well they might have done, if they had survived.
Under what terms or circumstances does that survival come about? A surviving south Vietnam, you argue, could have been South Korea. But then again, it could have ended up as Haiti or El Salvador. What's your POD, and how do events flow.
Go write a timeline. I say that in the kindest fashion possible. You have an interesting idea, it is testable, it needs research and development. Choose a POD, and then explore.
It would at least be an interesting project. There's a lot of "How can we win Vietnam" threads, but there's not a lot of threads exploring what happens after.