A second round of by-elections in the year took place to fill the vacancies following the resignations of another three Barisan Members of Parliament who were critical of Dr Lee Siew Choh's leadership. Chio Cheng Thun and Kow Kee Seng resigned on 8 January 1966 and were expelled from Barisan six days later. S. T. Bani resigned from both his seat and the party on 9 January 1966 while in detention. He was released a month later and retired from politics. All three PAP candidates won uncontested, something not witnessed since the Legislative and City Council by-elections of 1952 and 1953 respectively.

Writ of election: 23 February 1966 [Wed]
Nomination day: 1 March 1966 [Tue]
Members swearing-in: 21 April 1966 [Thu]

Electorate: 36,573

Election deposit: $500

Chua Chu Kang Crawford Paya Lebar

General Election 1963
By-Election 1965
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Next: By-Elections November 1966
By-Elections 1967
General Election 1968