Spread the mayo onto both slices of bread. Layer one slice with the ham, pineapple ring(s), and cheese. Close the sandwich and butter both sides. 

In a medium non-stick pan over medium-high heat, grill the sandwich for 2 to 3 minutes until the bottom is golden brown. Flip and continue to grill until the cheese is melted. 

Remove from heat and allow the sandwich to cool to room temperature before slicing in half and packing it inside the lunch container. 

Add the veggies and additional snacks to the container, but place them in separate compartments to keep the sandwich bread dry.