Hmm.. I only know that it's still not prevalent but eventually if you are qualified well it will happen. I see more of my Indian friends with local spouses , both male and female. They are all well qualified with good jobs. But yea I don't know the society well enough. Hope sons will.
One word of caution......
NS. You have not done NS yourself. So you probably dont understand it.
I will tell you that before I did NS I was brainwashed by the Singapore education system. SG is good. Racial harmony. Meritocracy. Equality.
But after serving NS my views changed a lot. I saw what Singapore truly is.
The problem with SG is that if you go to good schools you only mix with the same or similar social class. In NS if you get to OCS you will have the same experience too. But for those who might not go to OCS they can be posted to unit and have to serve with gangsters Pri 6 drop outs etc.
You also learn about scholar system rank etc.
I got disillusioned with Singapore AFTER I served NS. Which is ironic.
So that could happen for your sons. I hope they go OCS then they wont have this problem