She then continued in the council as an independent for a few months before resigning to contest in the 1959 Singaporean general election as the president of the Katong United Residents' Association (KURA).
As a member of the LSP, she was opposed to the People's Action Party's (PAP) plans for merging Singapore with the Federation of Malaya.
In her proposal, all prostitutes would be registered, young women would be prevented from engaging in such work and married men with wives in Singapore would be barred from entering brothels.
At an election rally, she claimed to have resigned as principal as she had been forced by the Ministry of Education to apologise to a "rich man's son" as a result of her reporting him for bullying, blaming the incident on the Labour Front.
[16] In December, Leon-Soh voted to re-elected Ong Eng Guan of the PAP as mayor, a move which "caused a storm in the party".
[17] She was "expelled" from the party in January of the following year after she was found guilty of "not owing allegiance to the organization" and continued with the council as an independent.
"[20] In March, she submitted a proposal to the health committee for rubbish collectors to be provided with several sets of uniforms and a shower with "disinfected water and soap" at the end of the work day.
Chief Administrative Officer P. C. Marcus called a special meeting in April to elect a new mayor while Leon-Soh maintained that she had already resigned, choosing not to attend.
"[24] Her opponents in the election were Tay Kum Sun of the PAP, Seow Peck Leng of the Singapore People's Alliance, who was also a "social leader" and a former headmistress, architect Wong Foo Nam of the Malaysian Chinese Association and Wee Soo Bee of the LSP.
[31] She had intended to stand as a candidate for the Hong Lim Constituency in the by-elections but was disqualified as her husband's name was listed on the 1959 electoral register for Mountbatten instead of her's.
"[33] In April, Lee Kuan Yew made a speech in which he claimed that an alliance between Leon-Soh and Ong Eng Guan, who had recently been expelled from the PAP and was contesting for the Hong Lim seat as an independent, was a possibility.
Leon-Soh responded by rejecting the accusation and challenging him to a debate on the matter, threatening the "exposure of the naked truth" of her disqualification.
[34] The following month, a petition was filed seeking the voiding of the Hong Lim by-election, which Ong had won, on the basis that she had been "improperly deprived of her democratic right" to contest in the election.
"[37] In January 1962, the Singapore Congress merged into the Liberal-Socialist Party, then headed by Wee Soo Bee, to "propagate liberal socialism under one banner.
[39] She met with Tunku Abdul Rahman in Kuala Lumpur in September in an attempt to delay the merger of Singapore with the Federation of Malaya.
"[41] Leon-Soh became the convenor of the Council of Joint Action, composed of five political parties all opposed to the merger of Singapore with the federation, which had been established in June.
"[42] In January 1963, Leon-Soh announced that the LSP would be organising an anti-Communist education campaign to "explain to the people why Communism is bad."
"[43] Leon-Soh organised talks in Tokyo between Indonesian President Sukarno and the Tengku in May 1963 on Indonesia's confrontation policies against Malaya.
"[46] Her opponents were Ng Yeow Chong of the PAP, Fung Yin Ching of the Barisan Sosialis and Lee Kim Chuan of the Singapore Alliance Party.
[49] In July 1971, she wrote and distributed a pamphlet defending Lee for taking action against the Singapore Herald, the Eastern Sun and the Nanyang Siang Pau.
[2] She married Leon-Soh Yew Leong, an executive member of the SC and then the LSP and the director and secretary of a mining company.