Try Air Asia, their prices are very reasonable. They also fly from Singapore to Bangkok.
BTW, I assume your daughter has got her immunizations against typhoid, hepatitis etc. and knows about how to keep from getting sick when eating in developing countries (peel it, cook it, boil it, or forget it)? Singapore is very hygienic, BUT Cambodia and Thailand are NOT.
2. becaureful salad which the vegetable washed by normal water.
3.becareful seafood even it's cooked ( esp. shrimp which has not taken inside stuff )