Is it wise to start investing (those long term ie: index, ETFs etc) while having student loans debt or should I payoff my student loans first before investing?

You should watch Dave Ramsey total money makeover. In short, better clear all your debts first.

In my view, it depends on the interest rate and the amount of the student loans. If you are still clearing your student loans, means you are young. Time is your greatest asset.

If the interest rate is not too high i.e. CPF education loan, you could split between the loan repayment and some investment.

No doubt you can focus on clearing your loans first but the opportunity cost is the time. Not sure how long you expect to take to clear all but I think typically is one to two years?

Myself, I split between the minimum payment to the CPF education loan and doing some investments for a couple of years. Took longer to repay the loan but some of my US stock returns have grown many times more than the loan interest rate over time. It’s tough but cannot say I regretted doing it.

You have to make your own decision. Do consider your cash flow first and always strive to improve your money making ability.