Teh O Limau Ais is iced black tea with calamansi lime and sugar, no condensed milk involved. That is exactly why it is lighter than teh tarik, which can clock 130 to 180 calories from condensed milk alone. At 70 calories for a standard glass, it is honestly one of the better drink choices at a mamak. The problem is the word 'standard' does different things in different shops. Some hawkers have a heavy hand with the sugar, and a manis-heavy pour can push you to 100 calories easily. These numbers are estimates, bro, there is no lab testing happening here, so treat them as a ballpark.
What actually moves the calorie count is purely the sugar. The tea and lime are basically free calories. About three and a half teaspoons of sugar gets you to 70 calories. Four teaspoons lands at 100. One and a half teaspoons (kurang manis) puts you at about 40. If you are tracking, just say kurang manis every single time and you shave off 30 calories per glass. Over a day of two or three drinks, that adds up. Nothing else changes here, no oil, no protein, no noodle swap to worry about.