LKY said so in his biography but nothing to do with China. LKY wanted status quo for all Malayans regardless of race and together with West Malaysia, Chinese formed a compelling percentage of the population. After instigation a couple of racial conflicts, Malaysia had no choice but to force Singapore out which is what LKY wanted; West Malaysia was betrayed by LKY.
LKY has a history of betraying it's ruler to be the ruler himself - betrayed the English to work for the Japanese, betrayed the Japanese to work for the Chinese, betrayed the Chinese to work for the Malays, betrayed the Malays to get Singapore.
Singapore was not defenceless. It has all the proper infrastructure and favourable terms. LKY told all the reports and news agency not to publish any photos of him smiling. The crying scene on TV became famous but it was all an act. These were based on released dockets from British intelligence.