So it is indeed insurance bought by the bank that provides the guarantee of $20K.
Some here presume that it is the singapore government who is footing the bill.
Actually it is the depositors who are footing the bill.
So if the insurance amount is increased to $100,000 then the premiums paid by the bank will be higher and the amount charged to bank customers be higher too.
Since the POSB was taken over by DBS, there is no longer any bank who offered guaranteed deposits.
All in all, guarantee or no guarantee, the safest bank in singapore is still DBS because so long as the singapore government does not collapse, dbs will not collapse.
If we consider that the US government is virtually bankrupt, surviving only by the grace of other nations to buy their bonds, DBS is a far better choice than US banks.