Possibly this one:
Who have this passport?
Why is it useless?
This map shows you how useless it is; you can only use it to enter one small country, in green.
Previously, Singapore had a passport which could only be used to enter West Malaysia, introduced 1967, two years after its separation from Malaysia, which was scrapped in 1999.
In order to enter East Malaysia, however, Singapore citizens had to have a full passport, while Malaysians resident in West Malaysia also needed passports.