Watch the cart for 30 seconds and you see where the calories are. The cook drops a lump of margarine the size of a golf ball on the griddle, and it all goes into the dough. That is 15g of pure fat, 110 calories, before the banana touches it. The dough itself is 80g of white flour made with oil and egg, another 240. Then the condensed milk goes on with a heavy hand, 20g for 65 calories, and a spoon of white sugar for 20 more. The banana is the healthiest thing on the plate and it is 14% of the total.
The number climbs fast with the extras. An egg cracked into the dough adds 75. Chocolate sauce or Nutella is 100 for the drizzle. Roti gluay kai with chocolate is 650 to 700 calories, more than a plate of pad kra pao with rice. It is a 10 minute walk to buy and 3 minutes to eat, and it comes after dinner, not instead of it.
A plain roti with nothing on it is about 350 and it is genuinely good, crisp and salty. If you want the banana, ask for no sugar on top (mai sai nam tan) and the vendor skips the white sugar and often goes lighter on the condensed milk too. That puts banana roti at about 430. Still a dessert, but 100 calories less than the default, and you did not have to give anything up that you would actually miss.