I met a Singaporean recently, and in our conversations he told me that “Singaporeans have sacrificed personal freedoms for their economic prosperity, but nobody is complaining.” Is this true?

It may be true but it may not be bad. I value stability over freedom of speech and full autonomy over finances (e.g. no CPF).

I'm not sure if other countries (especially countries which are run by democracy) should do the same and risk irritating the citizens.

What does personal freedom encompass? For me, personal freedom includes freedom to walk on the streets late at night and not worry about getting robbed. And I value this freedom (low crime due to efficient enforcement plus economic prosperity) more than freedom of speech or freedom to hold protests.