It is a concern because when a country's currency depreciates, inflation rises because imports will all cost more unless the government is subsidising the whole system.
If the the whole economy is propped up by subsidies, it's a matter of time before things come to head and the currency collapses.
If you think interest rates are the only indicator that matters, why don't you convert all your SGD to
Malawi $ and earn 25% straight away.
A $100,000 term deposit will earn you $25,000 per year.