There is a separate musollah for muslimah and muslimin available at RWS (The Forum, Level B1) near to The Streats. 
Prayer mats and telekung are available. Qibla sign and ablution area provided as well. 

Contributed by Brother Jeffri

Please note that the unofficial prayer area at level 4R, near to the library no longer exists. 

There is a new unofficial prayer area at the staircase on level 3 of the carpark.

From the Serangoon MRT (CC13/NE12),
1. Take Exit G which will lead you to Level B2 of NEX.
2. Take the lift/escalator up to Level 3 of the NEX mall and walk towards the Fairprice Xtra (#03-42) Exit.  
3. On the left of the Fairprice Xtra (#03-42) Exit is the connecting bridge leading to the Carpark Level 4.
4. Walk down the bridge and turn right and walk till the end of the Carpark (near to the trolley bay). Please be careful of the vehicles. 
5. You will see a ramp leading down to Level 3 Carpark with more trolleys. Walk down the ramp and on the right of lot 195 is the staircase with sign 'Smoke Stop Lobby Staircase 10'. The unofficial prayer area is located just behind that door and shared for both muslimah and muslimin. 

There is a Qibla sign and a prayer mat available. Please bring your own telekung. 
For ablution, you would have to go to the nearest toilet in NEX mall before making your way to the unofficial prayer area.

The address of the restaurant is: #01-07 HometeamNS Balestier. 
There is a musollah in the restaurant, please note that this is only for customers. For more information, the musollah can be found in this facebook video at timestamp 2:17.

There is an ablution area inside the prayer room. Separate prayer room for men and women. No air-con, only fan. Please bring your own telekung and prayer mat just in case, as we are not sure if these are provided. 
For assistance, please ask the staff.

Contributed by Sister Nisaa

There are 2 new unofficial prayer areas in the main wing/building (not new wing). 
Unofficial Prayer Area #1:  Level 5 (Exit Door at the lift lobby between Tempur #05-23 & Hooga #05-04/05)
1. From Dhoby Ghaut MRT (Exit B), you will be lead to B2 of the main building/wing. Take the lift/escalator up to level 5. If you are coming from the main wing entrance of Plaza Singapura on the ground level, take the lift/escalator up to level 5. 
2. Between Tempur #05-23 & Hooga #05-04/05, you will be an Exit Door in the middle of the lift lobby (it may be hidden behind the sign so you'd have to walk around it).  
3. Push the Exit Door The shared unofficial prayer area for muslimah and muslimin is located there. Kiblat sign is available. Please bring your own prayer mat and telekung. Ablution can be done at the toilets just beside the lift lobby.

Unofficial Prayer Area #2: Level 6 (Exit Door between Kopitiam #06-15/20 and Yamaha #06-01)
1. From Dhoby Ghaut MRT (Exit B), you will be lead to B2 of the main building/wing. Take the lift/escalator up to level 6. If you are coming from the main wing entrance of Plaza Singapura on the ground level, take the lift/escalator up to level 6. 
2. Between Kopitiam #06-15/20 and Yamaha #06-01, you will be a corridor leading to a lift lobby. 
3. Just before the lift lobby are 2 Exit Doors, push the Exit Door on the right. The shared unofficial prayer area for muslimah and muslimin is located there. Prayer mat available and kiblat. Please bring your own telekung. Ablution can be done at the toilets near to Kopitiam/Nail Palace which is towards the carpark direction.

There are 2 unofficial prayer areas in Parkway Parade. ​

Unofficial Prayer Area #1: Level 1, near to toilets beside Bata/Price Breaker
1. From the main entrance, walk straight and turn right at The Hour Glass and walk towards the toilets. You will see Bata/Fortune/Liho. 
2. Walk to the toilets and you can take ablution here. Once you've done your ablution, walk further down the corridor and on the right will be the staircase D, push the door. The unofficial prayer area is under the staircase. 
It is a shared unofficial prayer area for muslimah and muslimin. There is a qiblat, telekung and prayer mat available.

Unofficial Prayer Area #2: Level 3, near to the ATMs opposite Fairprice Extra
1. From the main entrance, take the lift/staircase to level 3 and walk towards ATMs opposite Fairprice Extra. 
2. There is a door leading to staircase F, push the door and the unofficial prayer area is located there. It is a shared unofficial prayer area for muslimah and muslimin. There is a qiblat and prayer mat available. For muslimah, please bring your own telekung. 
Ablution can be done at the toilets nearby, just down the corridor, just past the office building lift lobby.