MEATBALLS: Combine the mince, ground coriander, ground cumin, chopped coriander, sweet chilli sauce, egg, 2 T olive oil in a small bowl. Mix well. Wet hands and roll teaspoons of mixture into balls. Heat oil in pan, cook meatballs until brown all over and cooked through. Drain on absorbent paper.
DRESSING: combine the 2 T olive oil, brown sugar, lemon rind, lemon juice, red chilli, chopped mint, Thai fish sauce in another bowl.
Add two thirds of the dressing to the meatballs in a bowl; toss well.
Combine spinach, tomato, onion and cucumber in a bowl. Add meatballs and remaining dressing and toss gently to combine.