Possible Clues:

• Philosopher ___-tzu
• Language of Southeast Asia
• Chinese philosopher ___-tzu
• It's spoken in Vientiane
• Thai neighbor
• Language akin to Thai
• Language spoken in Vientiane
• 'The 7 Faces of Dr. --'
• "7 Faces of Dr. ___" (1964 movie)
• Language related to Thai