You can use Accurate Times to calculate the prayer times for your area. The time for fasting in Phnom Phen Cambodia today is from 5:31 a.m. to 7:28 p.m. (according to Hanafi madhab, taking summer time into account) but there are a number of variables to enter to get a more accurate time and the time will change slightly over the days. 5:31 a.m. is the time fajr starts so you need to stop eating/drinking etc. before this time. 7:28 p.m. is the time for maghrib and you should not delay breaking your fast (i.e. break it when you hear the adhan/the time has come).