That soil is not just moist. It is soggy. It's something to keep an eye on. It can't stay that wet for the tree to remain healthy. Indoors, the tree is not going to use as much water as it will outside.
Indoors, you will have to keep a constant eye on how and when you water--water when the tree needs it, not when you feel like it. BRT can't dry out, but they also can't stand constantly soggy soil. Watering is the hardest part of bonsai to master for all. It isn't an easy thing to learn and relies on temperature, light, humidity, etc. Needs differ day-to-day. Yellow leaves are a sign the tree is having to adjust to something, from being moved from a greenhouse to inside a house--that move has altered light, water and air circulation needs. The tree will likely continue to drop leaves as it tries to adjust...
All trees should be kept outdoors when possible, including tropical plants like this one. You don't say where you are located, but in general, tropical trees do best when kept outside from late spring to late summer (from the time springtime temperatures are consistently above 50 and into fall when average temps start dipping in the high 40's).
It's possible to keep some tropicals inside, but it's not easy. Extremely low light (and no, artificial "grow" lighting is inadequate, unless you invest in high-output LED, Halide, etc systems).