The boundaries of the Workers' Party-held constituencies of Aljunied, Hougang and Punggol East have been left intact, unlike the borders of the areas it has been eyeing.
Analysts said the likely reason for retaining the borders at the opposition-held constituencies is to quell talk of gerrymandering that benefits the ruling party.
In fact, the borders of Hougang and Potong Pasir, the two single- seat constituencies long held by opposition parties, had hardly been redrawn in the past few elections.
Potong Pasir, a Chiam See Tong stronghold since 1984, until it fell to the People's Action Party in the 2011 election, remains unchanged although it has only 17,389 voters. This is well below the 20,000 to 37,000 voters range the Electoral Boundaries Review Committee had set for a single-seat constituency.
Single-seat Hougang was WP chief Low Thia Khiang's bastion from 1991 until he left to lead a team to victory in Aljunied GRC in 2011. But it remains under WP control.
DECIDING WHERE TO CONTEST
A lot of the areas we had contested have been carved up... We have to study the report very carefully to decide which one we want to contest in.
WP NON-CONSTITUENCY MP GERALD GIAM
In 2013, the party brought Punggol East SMC into its fold in a by-election victory.
Analysts like sociologist Tan Ern Ser believe that any move to significantly change the boundaries of opposition constituencies would be politically untenable. It may even become an election issue, said Professor Tan of the National University of Singapore.
Indeed, in the 2011 General Election, Mr Low told Hougang residents in an open letter that his decision to leave to contest Aljunied GRC was spurred in part by what he called unfair changes in the electoral boundaries.
He criticised the moving of parts of Aljunied GRC where he said the WP had enjoyed good support, into Ang Mo Kio and Pasir Ris-Punggol GRCs. In turn, a part of Marine Parade GRC - the Kaki Bukit area - was absorbed into Aljunied GRC.
"So we're here to break through a GRC and let them learn a lesson," Mr Low had said then.
But the party is typically holding its cards close to its chest on what it plans to do in the next election.
Joo Chiat SMC, in which the WP lost by 388 votes, has been absorbed into Marine Parade GRC.
Moulmein-Kallang GRC, which it contested in 2011, has been split into four parts.
"A lot of the areas we had contested have been carved up," said the party's media chairman Gerald Giam, who is a Non-Constituency MP.
"We have to study the report very carefully to decide which one we want to contest in," he added.
However, Dr Gillian Koh, senior research fellow at the Institute of Policy Studies, said the WP is likely to continue to go for East Coast GRC and Fengshan SMC, which has been carved out of the old East Coast GRC.
Her reason: It did "fairly well" in East Coast in 2011.
"They may also move to the five-member Tampines GRC which is more manageable in terms of size than the six-member GRC of Pasir Ris-Punggol.
"WP is rather systematic in terms of trying to gun for areas that are contiguous to their bases as they focus on connecting directly with the ground," she added.
But with Joo Chiat SMC absorbed into Marine Parade GRC, Dr Koh wondered: "Will that cause the WP to move to the south and gun for that GRC?''
WP Non-Constituency MP Yee Jenn Jong hinted: "The party has expended a lot of effort every week on the ground in Joo Chiat SMC and in areas around it such as Marine Parade, parts of Joo Chiat outside the SMC, and Kembangan-Chai Chee. We will evaluate our options."
•Additional reporting by Chew Hui Min