How to create a passive income? I am a 19-Year-Old investor aiming to self-pay for my university (SMU ~$66K), after my NS (yet to enlist). Which investment paths should I look at?

Invest in yourself. You have to work. That will be your highest return on time and investment in your youth. There is no substitute for hard work. Keep expectations on investments low and do not expect it to fully fund your education. Making it your only source of cash inflow is risky and concentrated and certainly not guaranteed.

$100k by 25 is entirely possible. And it is very possible to accumulate that in one year. You do not need 6 years, even if you are in your early 20s. The question is, do you have what it takes to learn the skillsets required to achieve that? Stay humble, try new things, knock on doors, and opportunities will come.

As for investments, the only type of investments which can attract 100x of your money are extremely risky, you have to be prepared to lose the entire capital, even owing debt if you leverage and gear your moves. As such, it is often not recommended to assume such risks when you are younger. The safer path is to explore ways to increase your cash inflow with opportunities that requires very low capital requirements.

Hello! I am also a 19 year old. I am currently in my NS journey!

I think the major think you should look at would be to increase your income first. Thinking about a passive income is a great start. Since you have yet to enlist, you can start tutoring (popular and quite lucrative but not "passive").

There are also some other passive incomes you can start such as a small business! Maybe you can sell some second-hand goods, maybe you can sell some handcrafted goods. Then you can build your presence and slowly push your product.

I am glad to see my peers being financially woke haha

You can read some of my thoughts over at my blog.