In a small bowl, add mayo, ponzu sauce and wasabi paste; stir to blend. In a medium mixing bowl, add avocado, cucumber, tomatoes, green onions and pickled ginger; stir until well combined.
Pour in the wasabi aioli in the avocado mixture and gently stir until well mixed. Chill for 1 hour.
When ready to serve, take tuna fillet and pat it down with paper towel to remove any excess water and slice thinly. Place in a plate along with avocado mixture and rice crackers. Place two chives on top of the avocado mixture and serve immediately.