For the Thai Mango Dipping Sauce: In a blender, combine the diced mango, grated ginger, sweet Thai chili sauce, rice vinegar, and lime juice. Blend until smooth.
Add the chopped Thai basil and cilantro to the blender and pulse until chopped. Pour the sauce into a bowl, cover, and refrigerate until ready to serve.
For the Veggie Spring Rolls: Squeeze a little lime juice over the thinly sliced avocado to prevent browning.
Create an assembly line with all your prepared vegetables (cucumbers, lettuce, carrots, bell peppers) ready to go.
Fill a shallow dish with warm water. Take one rice paper sheet at a time and submerge it for 5 to 10 seconds until pliable. Remove and place on a flat surface.
Towards one end of the rice wrapper, layer with 1-2 slices of avocado, a small handful of fresh cilantro and mint, and a handful of mixed veggies. Sprinkle with salt and pepper. Fold both ends towards the center and roll the sheet as tightly as you can without ripping. Place on a serving platter and cover with aluminum foil to prevent drying out.
Continue with the remaining ingredients, adding each prepared spring roll to the platter and keeping them covered with foil at all times.
Serve the spring rolls immediately with the chilled mango dipping sauce.