Her eloquence and charisma won over voters when she stood for election on a National Solidarity Party (NSP) ticket in 2011.
But despite party efforts to woo her back, Ms Nicole Seah told The Straits Times via e-mail yesterday that she is not rejoining the party, and will not stand for election.
NSP acting secretary-general Hazel Poa reacted last night, saying: "Nicole is a bright young lady with courage and conviction. It will be a pity if she leaves politics permanently. I hope she will return to Singapore politics after some time-out, regardless of whether it is back to NSP or another party. In the meantime, I wish her all the best."
Ms Seah, 28, was part of the NSP's five-member team in Marine Parade GRC in 2011. It won 43.4 per cent of the vote - the third-best opposition performance in a GRC - against the People's Action Party team, which included then Senior Minister Goh Chok Tong.
Ms Seah took a leave of absence from the NSP in 2013, and quit the party last year. She has moved to Bangkok for work, and also made her acting debut in the film 1965, which is now showing in cinemas.
Ms Poa said during a walkabout in MacPherson yesterday that the NSP had "initiated contact" with her on messaging service WhatsApp, but had yet to hear from her.
When contacted by The Straits Times, Ms Seah said: "I didn't receive any message on WhatsApp from NSP. Perhaps they messaged my Singapore number, which is not in use. I'm not rejoining NSP, and will not run for elections this time." She added that she is in touch with NSP assistant secretary-general Reno Fong and organising secretary Spencer Ng on Facebook.
MacPherson has been carved out as a single-seat ward from Marine Parade GRC for the next election.
Its MP is Ms Tin Pei Ling, 31, who was widely compared to Ms Seah in the 2011 election because of the relative closeness of their ages.
Yesterday, several residents were heard asking the party: "Where is Nicole Seah?"
Meanwhile, two potential NSP candidates said yesterday that Ms Seah inspired them to join politics.
They are real estate agent Eugene Yeo, 40, who wants to campaign on housing issues, and Ms Kevryn Lim, 26, a project director at events management and digital marketing firm EM.DM.
Ms Lim has drawn some criticism online because of her former career as a model.
But she said she was undaunted by the flak: "I'm quite proud of (my past) and it is not a shameful thing. Everybody has a past."