 The new Chief Minister , Lim Yew Hock , launched a crackdown on communist and leftist groups , imprisoning many trade union leaders and several pro @-@ communist members of the PAP under the Internal Security Act . The British government approved of Lim 's tough stance against communist agitators , and when a new round of talks was held beginning in March 1957 , they agreed to grant complete internal self @-@ government . A State of Singapore would be created , with its own citizenship . The Legislative Assembly would be expanded to fifty @-@ one members , entirely chosen by popular election , and the Prime Minister and cabinet would control all aspects of government except defense and foreign affairs . The governorship was replaced by a Yang di @-@ Pertuan Negara or head of state . In August 1958 , the State of Singapore Act was passed in the United Kingdom Parliament providing for the establishment of the State of Singapore . 
