Hello and welcome. I don't usually water by the immersion technique but more worrisome than how you are watering is how often. I'm guessing that the tree is potted in a medium that resembles conventional potting mix. This type of medium holds water longer than a bonsai mix which is very open and drains immediately. Your tree will need to be re-potted in order to ensure its long term health.
For now though concentrate on proper watering and placement. Indoors, a bright location is required or lacking that some form of supplemental lighting. Read [url=https://www.helpfulgardener.com/forum/viewtopic.php?t=1479]this[/url] for some tips on proper watering. Very quickly, let it dry out more before watering it again. If you have fertilized it recently don't worry about it until you see some signs of recovery. If you have not yet fertilized it you can, just make sure to follow the proper rates on the packaging.
For future reference you can also have a look at the other threads [url=https://www.helpfulgardener.com/forum/viewforum.php?f=36]here.[/url] The one on potting and soils should give yo some idea of what a proper bonsai medium generally consists of.