I don't really like mangos, you know the yellow ones, a sweet, sickly and soggy mess they generally turn out to be, although I do like mango chutney, but that's a different kettle of fish, but what to do with the un ripe dark green ones?
Now this I do like, not sure if they only do this in Thailand but got a feeling it's probably eaten with similar bits and pieces in other countries that grow mangos, each tree has so many fruits on it and such a long season that they got to get rid of them some way or other, we can only eat so much mango chutney 
So, take some green mangos such as these.

Wash and peel the skins off your mangos, now slice, easiest is to hit the stone with a big bladed knife and break the mango pieces off, now all you need is some sugar and ground chili powder, with your sliced mango dip into your mixed chili and sugar and eat away, delicious, there are also other dips you can make to go with your un-ripe mangos 

Mango Chutney Recipe
Ingredients
1 ripe but firm green mango (450 -500 g)
1 sticks cinnamon (about 2 inch)
2 whole cloves
1 tsp cumin seeds
1 tsp coriander seeds
2 cardamom pods, cracked
1 tsp ginger, grated
2-3 whole dry red chilies
1 clove garlic, crushed
3/4 cup demerara sugar (if you have access to Indian jaggery use 3/4 cup- 1 cup powdered jaggery depending on the sweetness)
1/2 cup vinegar
3/4 cup water
1 tsp salt
Method:
Cut the mango into 1 inch cubes and for chunky chutney, keep some pieces about 2 inch. If you are looking for smooth, cut them all in same size.
Using a piece of thin muslin cloth, tie up the spices into a bundle. Cook the mango, spices (in the muslin cloth), water, ginger and garlic until the mango is tender. Some pieces will disintegrate into the water. Takes about 10 minutes.
Add the vinegar, sugar, salt and dry chilies. I like to break 1 red chilly into flakes and keep 1 whole. If you want and are feeling adventurous you can go up on the chilies. The sugar requirement may also vary depending on the sweetness of your mango and personal preference. Feel free to reduce or add as per your liking.
Cook for about 30 -35 minutes until the chutney is thickened. Squeeze every bit you can from the cloth and discard it. Transfer to sterilized jars while still hot. Don’t put the lid, until the chutney cools. It keeps well for 4 weeks in the refrigerator.
How to Peel a Mango Thai Style
More Thai Recipes.
Thai Food For Newbies