Asked on 25 Mar 2019
Thanks for the question, there are in fact many who have the same query as you.
It really depends on the stock that you intend to buy. Talking about blue chips-wise, after the reduction in minimum purchase size of 1000 shares to 100 shares in 2015, it has significantly reduced the starting capital required.
Just head on to SGX.com, whatever prices you see at the Last Done column, multiply it by 100 and that is the minimum amount you're required to foot. However, do take note of the commissions per transaction which can be found here as done up by Seedly https://blog.seedly.sg/the-ultimate-cheatsheet-cheapest-stock-brokerage-in-singapore/
In a nutshell, if you utilise the CDP account a.k.a. Cash Account in brokerage firms, it costs minimum $25 or 0.28% (whichever is higher) per transaction excl. SGX fees. So all in all, if you were to buy and sell a stock, it'd cost a total of $60.
Now, if we look at DBS which is trading at $25.29 (as of time of writing), if one were to purchase the minimum amount, which is 100 shares, it'd be $25.29 x 100 = $2529. After addition of the commissions, in order to breakeven, you're required to sell DBS at $2589. Therefore, the share price has to rise approximately 3% before you can bag a profit.
The minimum amount of money is $100 a month for investment in STI ETF. Examples are the SPDR STI ETF or the Nikko AM STI ETF.
POSB investsaver allows you to buy into the STI ETF for as low as $100 a month. That's actually more diversified, and very affordable as compared to buying 1 lot (usually 100 shares x Price of stock) for a particular stock.