Even you dont need the letter of approval. Perhaps will make things easier, but I forgot to print mine (last minute packing/arrangements as usual) and no problem, I entered singapore as a tourist (30 days for spanish) and went to MoM in my first week here and got the pass.
The letter will avoid questions when inmigration sees that you enter SG with one-way ticket, but they just will tell you how serious offence is to stay longer than the legal time in SG as a tourist. After telling you that 100 times, you can enter in SG
