Is money used for investment income tax exempted?

If you are asking if your invested money are tax exempted or not. The answer will be they are not.

If you are asking about if the money you earned are taxable or not then it depends.
Capital gains are not taxable in singapore. Income from dividends, shares, etc are taxable too.

You may read more about it here https://www.iras.gov.sg/irashome/Individuals/Lo...

P.S. While capital gains are generally not taxable, the Inland Revenue Authority of Singapore (Iras) will also determine if the sellers are in fact trading in properties/shares by considering factors such as frequency of transactions and the holding period of the properties/shares.

You may read a news article related here

https://www.straitstimes.com/singapore/courts-c...

If I understand your question correctly, what you are referring is that
Example: you earn $100k

if you invest $10k, will your taxable income be $100k or $90k.

Answer: $100k taxable income.
Investments are not allowable business expense. You can read up more here.

https://www.iras.gov.sg/irashome/Businesses/Sel...

If you would like to get tax exemptions,

1. Contribute to your CPF

2. SA contribution

3. SRS contribution