The official Thai figure of 240 calories per cup surprises people because it sounds low for a coconut curry. It is low because a food court ladle is about 80ml of coconut milk and 50g of chicken. Restaurant green curry is a different animal: a full bowl with 150ml of thick coconut cream and 120g of chicken is closer to 480, which is the figure some Thai calorie tables list. Same dish, double the portion.
The rice is where the meal gets its size. A normal 200g plate of jasmine rice is 260 calories, so curry plus rice is about 500. Order it over khanom jeen (fermented rice noodles) and the noodles are lighter at about 165 for 150g, but stalls ladle far more curry over noodles than over rice, so that plate usually ends up heavier, around 560 to 620.
Green curry is one of the sweeter Thai curries. The name literally means sweet green curry, and there is usually 10 to 15g of palm sugar in a pot. That is not a huge number per bowl, but with the coconut fat it is why one bowl tastes like a treat and two bowls feel like dessert.