Application for travel document

Dear sir/madam,
Hope you are doing fine.
My daughter is 9 years old & is a Singaporean. My wife is a Chinese and currently is a Singapore citizen. My daughter used to apply for Travel Document 旅行证 issue from China Embassy when traveling to China & that is my wife was still holding the China passport. Since my wife is already a Singapore citizen, can i still apply for the Travel Document? How do i apply?
From what I understand, children under 12 years old need to apply for Travel Document even though they are holding a Singapore passport. Kindly correct me if i am wrong.
Appreciate you can advise.