Male yoga student is looking for cheap bed place in Singapore

Please note that renting out private residential space in Singapore is only allowed to holders of residence visa and only for periods of 6 months or more. You do not qualify for this.
If you cannot stay with your friend for free, you are limited to hotels, hostels and serviced apartments. Some hostels start at S$60/night for a single room, but you may want to budget S$80-100/night to get something half-decent.
Remark: Singapore is one place in the world where you do NOT want to break the rules! (And short-term private room offers you find on the Internet are anyway mostly scams.)

Thanks beppi for your reaction and clear advice. Do you know some good hostels that are decent and not too expensive?

I have never stayed in one myself, but I have heard (several years ago) good reviews of this one:
    http://www.sleepysams.com
The location is excellent and it looks nice from outside, that's as far as I can tell.
But any good guide book (e.g. Lonely Planet) will be able to show you more like this, and possibly more up-to-date information.