During her undergraduate and postgraduate studies, Lim did volunteer work with the Spastic Children's Association, Salvation Army Home for the Aged and University College Hospital.

[citation needed] In March 2006, Temasek Polytechnic modified its staffing policies to enable Lim to run as a candidate in the general election without having to resign her teaching position at the institution.

[9] During her term in Parliament, Lim spoke out against ministers' salaries,[10] and also against means testing in hospitals, which resulted in the PAP deferring a decision on this for a period of two years from 2006 to 2008.

[16] Lim expressed concerns about a proposed constitutional amendment introduced in April 2010[17] that would allow magistrates to hear what are called "first mentions" through video conferencing.

[18] She felt it failed to adequately assure accused people that they were allowed to complain to magistrates about injuries they had sustained or acts of misfeasance against them by the authorities.

[26] In the 2011 general election, Lim again contested in five-member team along with Pritam Singh, Chen Show Mao, Low Thia Khiang and Muhamad Faisal Manap in Aljunied GRC.

In her final election rally speech, Lim emphasised that contrary to the public's perception, there was "no glamour" in being an opposition MP, and that she was only "fighting to serve".

In addition, the defeat of the incumbent PAP team marked the first time in Singapore's electoral history that a serving cabinet minister lost his seat.

[citation needed] She has been assigned to look after the Serangoon ward previously held by the PAP's Lim Hwee Hua and has also been appointed Chairman of the combined Aljunied–Hougang Town Council.

[31] Lim further noted in her speech that Singapore was a co-sponsor of Bhutan's resolution in the United Nations entitled Happiness: Towards a holistic approach to development.

Lim's speech drew swift rebuttals from MPs of the ruling People's Action Party, including Prime Minister Lee Hsien Loong who suggested later in 2014 that it was impractical "to switch to a different metric – from GDP to GNH".

In 2012, Lim engaged in a heated debate with Law Minister K Shanmugam where she questioned if the judgement published by the Attorney-General's Chambers (AGC) with regards to the Woffles Wu speeding case had addressed public concerns on the equitability of Singapore's legal system.

This led to Lim filing an adjournment motion in Parliament titled Safeguarding the Public Interest in Town Council Management, which she withdrew after the government announced it will conduct a review on the issue.

[41] Lim further expressed concerns with regards to newly imposed liquor control regulations, as well as policing resources and manpower required to handle such occurrences.

[43] Lim expressed support for the Pioneer Generation Package rolled out by the government in 2014, but raised concerns with regards to the MediShield Life scheme, particularly for Singaporeans who are already on private medical insurance or those living abroad.

[44] Less than a month before election day on 12 August 2015, Lim set up her Instagram account with the first post showing a photo of herself eating oyster omelette at Fengshan Hawker Centre.

[45][46] A media frenzy and large public reaction ensued, with rumours circulating that Lim was considering a move to contest the election in Fengshan SMC.

Speaking to the media just hours after the election results on the sidelines of a thank you parade, Lim questioned if "voters don't want too much opposition in Parliament".

She added that the bill provides "draconian enforcement muscle" to the government, with the Minister using "a sledgehammer to kill an ant ... we are one step closer to being a police state".

Focusing her speech on potential conflicts of interest, Lim revealed that Singapore's current Attorney-General (AG) Lucien Wong represented the PM as his personal lawyer in the dispute involving the house.

[60] Lim has suggested since 2006 that a reversion back to the system where the president is appointed by Parliament would "naturally take care of any concerns of minority representation and would not be regressive".

[63] This subsequently led to former presidential candidate and ex-PAP MP Tan Cheng Bock filing a suit in the High Court on whether the government's decision to start the count from President Wee was correct and in accordance with the constitution.

She accused the government — particularly PM Lee, DPM Teo, and Minister Chan — of attempting to "confuse and distract", and misleading Parliament by "merely using the AGC's advice as a cover to avoid full Parliamentary debate on why the count was not starting from President Ong Teng Cheong".

"[72] In opposing the renewal of the Criminal Law (Temporary Provisions) Act (CLTPA) on 6 February 2018, Lim questioned the premature renewal of the bill and said that the government had "gone too far" with the additional provisions, charging that the addition of a finality clause in the act to make the Minister's decision on whether to detain someone without trial final was an “attempt to make the Minister (for Home Affairs) all-powerful”.

[75] Lim branded the bill "untenable" and accused the Minister of attempting to be "a global policeman with no equal in the world" after it was revealed that individuals who commit criminal activities outside Singapore may now be detained under the CLTPA as well, as in the case of Dan Tan.

[83] Lim fired back, "The Government can rebut our speeches robustly, that's fine, but I don't think I'm disentitled to come to Parliament to advance honestly held beliefs or suspicions".

Many online commentators on Channel NewsAsia's Facebook page, citing the presence of parliamentary privilege and the fact that it was an elected MP's duty to voice out the concerns of the public, were largely unconvinced by Shanmugam's accusations and saw no issue with Lim's statement.

[93] I do not accept the over-characterisation the PAP MPs have put on my words and intentions, based on their own interpretation borne out of overactive imaginations and over sensitivity.

Lim therefore stated plainly that she was not going to offer any apology and will not retract any of her statements as she believed she was doing her “constitutional role” as an elected MP to “convey ground concerns, reactions and confusion".

While speaking at the CANA Catholic Centre Talk of the Town event in 2014, Lim said she tries "to read the bible everyday" but prefers to keep her faith private, adding that it is "not my nature to evangelise" as others may already have their own religion in which they take comfort in.