Prepare the jelly: If using agar agar powder, dissolve it in water according to package instructions. Add food coloring to create red, green, and yellow jellies separately. Pour into shallow pans and refrigerate until firm, about 2 hours. Once set, cut into small cubes.

Prepare the fruits: Drain canned jackfruit and cut into bite-sized pieces. Drain canned longan or lychee. If using fresh fruits, peel and prepare accordingly. Set aside in a large bowl.

Make the coconut milk mixture: In a saucepan, combine coconut milk, sugar, and a pinch of salt. Heat over medium-low heat, stirring until sugar dissolves completely. Do not boil. Remove from heat and let cool to room temperature, then refrigerate until cold.

Prepare crushed ice: Use a blender or ice crusher to create fine crushed ice. Keep in freezer until ready to serve.

Assemble individual servings: In tall glasses or bowls, add a generous amount of crushed ice as the base. Layer jelly cubes in different colors for visual appeal.

Add the fruits: Distribute jackfruit pieces, longan, and any other fruits evenly among the glasses.

Pour the coconut mixture: Slowly pour the chilled sweetened coconut milk over the ice and fruits, filling about three-quarters of the glass.

Final touches: Top with additional coconut milk if needed. Optionally garnish with fresh basil seeds or pomegranate seeds for extra texture.

Serve immediately: Chè Thái is best enjoyed fresh and cold. Provide long spoons so diners can mix ingredients as they eat.