http://www.elections.gov.sg/gazette%5CG_RE2011%5CNames%20and%20Polling%20Districts%20of%20Electoral%20Divisions.pdf#zoom=100 shows the polling districts for "Punggol East". Which are PN38, PN39, PN40, PN41, PN42, PN48, PN49, PN53, PN54, PN55
To find out if you "belong" to "Punggol East", the easy way is to login at
http://www.elections.gov.sg/online.htmlLook at "ED/PD". If it shows PE-PNxx thats "Punggol East", if it shows PN-PNxx that's "Pasir Ris Punggol GRC".
If you want to do it the hard way,
Then look at
http://www.elections.gov.sg/gazette%5CG_RE2011%5CBoundaries%20of%20Altered%20Polling%20District.pdf which shows which areas falls under those polling districts,
PN38 The area bounded by Rivervale Drive, Sengkang East
Way, Sengkang East Drive, Tampines Expressway,
Sungei Serangoon and imaginary boundary between
Block Nos. 121D, 121B, 121 and Block Nos. 120B,
120A (common boundary of PN38 and PN55).
PN39 The area bounded by Sengkang East Way, Rivervale
Crescent, imaginary boundary between Block Nos.
142, 143, 143A, 146 and Block Nos. 148, 147, 146A
(common boundary of PN39 and PN40), Rivervale
Drive, Rivervale Crescent, south-eastern fringe of
Block Nos. 183C and 183D, Tampines Expressway and
Sengkang East Drive.
PN40 The area bounded by Rivervale Crescent, imaginary
boundary between Block Nos. 183A, 183, 183B, 183C
and Block Nos. 184A, 184, 183D (common boundary
of PN40 and PN41), south-eastern fringe of Block No.
183C, Rivervale Crescent, Rivervale Drive and
another imaginary boundary as described in PN39
(common boundary of PN40 and PN39).
PN41 The area bounded by Rivervale Drive, imaginary
boundary between Block Nos. 186C, 186D, 187A,
187B and Rivervale Primary School, Block Nos. 188A,
188B (common boundary of PN41 and PN42),
Tampines Expressway, south-eastern fringe of Block
No. 183D, another imaginary boundary as described in
PN40 (common boundary of PN41 and PN40) and
Rivervale Crescent.
PN42 The area bounded by Punggol Road, Tampines
Expressway, imaginary boundary as described in PN41
(common boundary of PN42 and PN41) and Rivervale
Drive.
PN48 The area bounded by Rivervale Drive, Rivervale
Crescent, Sengkang East Way and Punggol Road.
PN49 The area bounded by Sengkang East Way, Rivervale
Drive, imaginary boundary between Block Nos. 135,
138, 139, 140, 131, 125 and Block Nos. 134, 133A, 133
(common boundary of PN49 and PN53), Rivervale
Street and Punggol Road.
PN53 The area bounded by Punggol Road, Rivervale Street,
imaginary boundary as described in PN49 (common
boundary of PN53 and PN49), Rivervale Drive and
Rivervale Lane.
PN54 The area bounded by Rivervale Lane, Rivervale
Drive, Sengkang East Avenue and Punggol Road.
PN55 The area bounded by Rivervale Drive, imaginary
boundary as described in PN38 (common boundary of
PN55 and PN38), Sungei Serangoon, the production of
Sengkang East Avenue and Sengkang East Avenue.