Browsing through Elections in Singapore written by Pugalenthi Sr and published in 1996, I was struck by this passage, where he writes about the 1959 elections, which brought Senior Minister Lee Kuan Yew to power:
He said the citizenship laws had deliberately been made very liberal to allow Commonwealth citizens to take up citizenship after a stay of only two years here. This was aimed at providing the large number of Britons here a say in local politics. But most of these Britons had no intention of making this their homeland and would "scoot off" as soon as things "got hot here".
The book does not give any references.
But Mr Lee and his People's Action Party in those days did strike a chill in the hearts of expatriates, according to the historian Constance Mary Turnbull. In A History of Modern Singapore (1819 – 2005), she describes the aftermath of the PAP victory in the 1959 elections, when PAP won 43 of the 51 seats (see the Elections Department page and Wikipedia: total voters 586,098, voter turnout 527,919 or 92.9%). Turnbull writes: