Mr David Ong had just begun his second term as an MP when he resigned. But his time in the grassroots movement goes back to the late 1990s, when he was a grassroots leader in Kreta Ayer.
First fielded in Jurong GRC at age 50, he was the second-oldest of the People's Action Party's new faces in the 2011 General Election.
Mr Ong is managing director of RedDot Publishing, which produces publications for the tourism industry. But his grassroots background drew more attention when he was a new candidate.
He was then chairman of the Citizens Consultative Committee in Jalan Besar GRC's Kreta Ayer-Kim Seng ward.
His three sons - then aged 12, 14 and 16 - occasionally accompanied him to community events, he revealed in an interview ahead of the 2011 elections.
Mr Ong's dedication to residents as their MP was commended by PAP leaders yesterday.
Said Deputy Prime Minister Tharman Shanmugaratnam: "Mr David Ong has worked extremely hard for Bukit Batok.
"He's a really hard-working MP. He spends four to five times a week in Bukit Batok - weekends, weekdays, nights."
Prime Minister Lee Hsien Loong, replying to Mr Ong's letter of resignation, noted that he had "served diligently as an MP" in Jurong GRC and after his ward was carved out as a single seat last year.
"As an MP, you worked hard to strengthen the Bukit Batok community, building up a team of volunteers and community partners to help residents in need," he said.
He cited programmes that Mr Ong introduced to help needy families with groceries, provide job and healthcare support, and give a fresh start to individuals with repeated problems.
Mr Lee also noted how Mr Ong spoke up for the elderly in his parliamentary speeches - on issues such as the retirement age and Central Provident Fund policy.
Back in 2011, Mr Ong was chairman of the People's Association's Active Ageing Council.
Mr Lee also noted Mr Ong's contributions outside his MP duties, such as being involved in organising the annual River Hongbao Festival - something he had been doing even before joining politics.