Limau ais is just lime, water, ice and sugar. No milk, no cream, nothing fatty. The only calories come from the sugar syrup they squeeze in, around 100 worth. Compared to a teh ais or a Milo, this is a featherweight.
The catch is some stalls go heavy on the sugar to balance the sour, so it can creep higher than you think. Just say kurang manis. The lime keeps it refreshing even with way less sugar, so you barely notice the difference.