China A-shares are normally traded in CNY. However, you do not need to hold CNY to trade them.
You can buy these stocks directly from any of your currency accounts, such as SGD or USD. When you trade, the system automatically converts the funds. Read more in Trading when your (sub-)account currency differs from the instrument currency.
You can also choose to open a sub-account in CNH and trade China A-shares there.
Read more in About sub-account