Saint and Monk's AC bonus

Question

If someone with saint template chooses to become a monk would they gain double of their wisdom modifier as AC or is it a one time only bonus that does not stack?

Answer 1

They stack.

The Saint template says, regarding its Armour Class ability:

Armor Class: A saint gains an insight bonus to AC equal to the character's Wisdom bonus. (Book of Exalted Deed, pg 185, Creating a Saint. Emphasis mine.)

The Monk class says, regarding its Armour Class ability:

AC Bonus (Ex): When unarmored and unencumbered, the monk adds her Wisdom bonus (if any) to her AC. In addition, a monk gains a +1 bonus to AC at 5th level. This bonus increases by 1 for every five monk levels thereafter (+2 at 10th, +3 at 15th, and +4 at 20th level).
These bonuses to AC apply even against touch attacks or when the monk is flat-footed. She loses these bonuses when she is immobilized or helpless, when she wears any armor, when she carries a shield, or when she carries a medium or heavy load.

You'll notice a distinct lack of type on the bonus added by the Monk's ability: as such, it is not an insight bonus to AC, and therefore does not interfere with also gaining an insight bonus to AC.