Currency exchange aka forex is like stock will go up and down. For SGD it is a strong currency.
I prefer to characterize the Singapore dollar as a
quality currency. "Strong" implies a particular exchange rate, or exchange rate trajectory. That's certainly not a given. In the past the Singapore dollar has fallen significantly in value relative to major currencies. Of course that bit of history could repeat itself.
In my view it's unwise to peg most or all of your financial future to
any single currency, even if it's among the world's quality currencies. Inflation and devaluations are possible, of course.
Also, the exchange rate on its own, in isolation, isn't the whole story. As long as you're compensated (or more than compensated) for any losses due to exchange rate movements you can still come out ahead. Let's suppose you're comparing 12 month T-bills in two currencies: Currency A and Currency B. And your lifestyle is chiefly based in Currency B, let's assume. Here's what happens in this example (net figures, after costs):
Currency A: 5.0% interest rate, but reduced to 3.0% because of an exchange rate loss
Currency B: 2.5% interest rate (and of course 0% exchange rate loss)
Which T-bill is better? Of course it's the foreign currency T-bill in this example. The higher interest rate more than compensates you for the loss due to exchange rate movement. (And we're assuming here the risk profiles for these T-bills are comparable.)
For MYR forever weak at least in my lifetime.
Possibly, but it's also probably true that ringgit interest rates, bond yields, etc. have been higher on average than rates/yields on comparable Singapore dollar vehicles. Obviously the Malaysian ringgit has lost value relative to the Singapore dollar since the currencies separated (then on a 1:1 exchange basis). Probably the higher average ringgit interest rates/bond yields have not been enough to compensate for the exchange rate loss relative to the Singapore dollar, although it's partial compensation.
"Be careful what you wish for," though, if you're wishing for a strong Singapore dollar. A strong domestic currency hurts exports, and it makes Singapore comparatively less attractive as a base of operations for global multinational companies. It means Singapore is comparatively less attractive as an international convention site since it's priced out of competition against Madrid, Tokyo, Seoul, etc. Singapore is a small, open economy heavily reliant on trade. If the currency is too strong then it's harder for Singapore to compete internationally.