The "best" time to water is arguably early in the morning, before your bonsai begins its day of photosynthetic activities.
However, it is important to be vigilant about its watering needs throughout the day, especially during the summer. It makes no sense to schedule watering late in the morning, if you know that five days a week you're going to be out the door by 7 AM
Location of the plant :-
A bonsai should be placed where it is viewed. Where a bonsai is placed is also where it grows. A bonsai must be placed in favorable environment. The location should receive sufficient sunshine, be well ventilated, and have properly maintained temperature. Indeed, such environment is healthy for humans as well as the plant.