What are low risk investments for beginners with no time to watch over the investments?

For investments, I would recommend doing a regular savings plan via POSB investsaver or FSMOne. You only need to set it up once, and the rest is automatic. Also, don't forgot about optimizing your savings account using high yield interest accounts like DBS Multiplier / OCBC360 . Standard Chartered Jumpstart. They can potentially yield 1.85% or higher.

This is just my opnion, but i would look at a company/companies that i am familar with in a business that i think will be around for a long time and are paying regular dividends to buy into. It is not low-risk (but what do you mean by low risk anyways). Even if you have no time, you should be able to look at the counter every year to reevaluate. The other 'low risk' investments are really low yielding and arguable are not investments - just parking your money for slightly higher yeild vs leaving it in deposits eg SSB.
So i would say: SGX listed blue chips with decent dividend yield

the reason is, you are starting out so you wouldnt want to be exposed to ccy risk. Blue chips usually are household names and their businesses are familar to you. They are more stable and usually are cash cows which will not scare you unduly due to volatility. Lastly, dividend yields are very encouraging for starting investors who get to see some returns credited back to your account! Hope this helps. You can choose to DCA into an STI index through a RSP as well, but that's abit more passive

Fixed deposits, Singapore savings bonds, Bank's high interest savings accounts. CPF but long locked in time.

These are the safest ones in SG.

Higher the risk, higher the rewards. Invest according to your expectation.

No risk : Cash / Term deposits

Low risk : Bonds / Fixed Interest security

Medium risk : Managed / Mutual funds / Unit trust

High Risk : Shares

Very high risk : derivratives