How best to fly to Xian

There is direct flight from Singapore to Xian, so you can take the flight. The leaving time from Singapore is at 03:00. If you do not want to take the direct flight, you can fly to Shanghai first and then to Xian.
As for the Tong Lai Soon, there is not a branch in Xian. If you want to eat Muslim food in Xian, you do not worry about it. There are many muslim food in Xian, among which Moslem Street is the most famous. You can eat different muslim food there.