How often should I water Premna bonsai?

The pot's size and the plant's size also affect watering. I usually check the soil by pressing it a little. Is it dry? If so, you can probably water it right away, but don't let there be puddles on the surface. I always provide planting media with good drainage, such as soil, and I choose pots with good drainage, too.

You can give it some water about once every two weeks and just check there's no puddle on the surface of the soil.