you; yourselfตัวเธอ emphasizes the person being referred to and can sometimes literally mean “your body,” depending on context. เธอ is an informal or intimate way to say “you.”
TH: ฉันอยากให้ตัวเธอรู้ว่าฉันอยู่ข้างเธอเสมอ
EN: I want you to know that I’ll always be by your side.