I think somebody already mentioned it, but bear in mind that if you're holding an asset you're holding an asset, not the currency(ies) it is denominated in.
OK, with that important point in mind, you can get some "free" currency benefits if you are using Singapore
dollar cost averaging to acquire assets. That is, you buy a fixed S$X per month (on the same day of the month) of your investment assets, month in month out, for years, preferably decades. If you can step up that X figure to sustain a higher level of dollar cost averaging, great, but consistency counts. Dollar cost averaging means you will naturally, automatically buy more of that asset when its Singapore dollar price is relatively low (which could be due to currency effects) and less of that asset when its Singapore dollar price relatively high.
Transaction costs can be higher to dollar cost average, especially for smaller dollar amounts, so you have to balance any higher transaction costs against the benefits of dollar cost averaging. Variations are possible, such as dollar cost averaging on a bimonthly basis, to mitigate any such higher transaction costs.
By the way, EWS is the ticker symbol for
an exchange traded fund that tracks a Singapore stock market index (MSCI, but it's very similar to the STI). EWS is traded in U.S. markets. If you're a U.S. person and wish to have an index of Singapore stocks in your portfolio -- i.e. you want to make a bet on Singapore equities as a whole -- it's a reasonable option. For everyone else, including those concerned about exchange rates, I wouldn't recommend it.
FYI, the U.S. S&P 500 stock index is up over 15% over the past year in U.S. dollar terms, as I write this, and excluding dividends. The SGD-USD currency change is small compared to that big movement. When you're investing in stocks, you're investing in a class of assets that typically has much greater volatility than the SGD-USD path. So if you're concerned about SGD-USD volatility, you should be that much
more concerned about stock market volatility. And if this stuff feels too risky for you, then now would probably be a good time to collect your profits and move your money to something like Singapore Savings Bonds and Singapore Government Securities.
Singapore, and the Singapore currency zone, are
small. Very, very small. Something like 99% of the ways you can invest involve assets outside Singapore. This is just how it goes. Long-term investing with dollar cost averaging is the primary, prudent mechanism to deal with volatility. Or...stick to CPF, SSBs, and SGSs.

Or some of both, which is what I do.