Which Amesha Spenta represents 'Good Thought'?

The Amesha Spenta that represents “Good Thought” is Vohu Manah.

Vohu Manah is an Avestan expression usually translated as “Good Thought,” “Good Mind,” or “Good Purpose.” It describes the constructive state of mind that helps a person choose wisely and fulfill moral responsibilities. Its opposite is Aka Manah, or evil mind and purpose.

In later Zoroastrian tradition, Vohu Manah is one of the seven Amesha Spentas, divine emanations associated with Ahura Mazda. It is linked especially with animal creation, particularly cattle. The name comes from vohu, meaning good, and manah, meaning mind, thought, or purpose; the latter is related to Sanskrit manas.

The concept appears in the Gathas, the oldest hymns of the Avesta, though scholars note that the term is not always used there as a fixed proper name. In later Persian, Vohu Manah became Bahman, and the eleventh month of the Iranian calendar bears that name. Haurvatat means wholeness, Armaiti devotion, and Asha truth or righteousness.