รู้แน่ชัดว่า

know for certain that

→ รู้
phrase Rare #15,604
know for certain that Often followed by a clause; when that clause contains a question word such as who, what, or where, it can mean “know exactly who/what/where.”
TH: ฉันรู้แน่ชัดว่าเขาอยู่ที่ไหน
EN: I know exactly where he is.