Hey,
I am of the opinion that you should just leave it alone. #1 if you start messing with a plants that small you are likely to kill them all. say you have 3 or 4 clustered together and you try to space them, i think you will kill two in the process. if you just leave them, 1 of them will probably survive anyway. maybe two of them will make it. so, i think thinning is a waste of your time.
also, if you think about it, when you're out digging wild ginseng (assuming you hunt ginseng) many times they are growing this way in nature. I have dug roots that are clustered together like they were one big root, but are actually two or three different plants.
I have the same problem while planting ginseng. it's hard to plant by hand and not drop a few seeds in the same spot. I find that they usually grow just fine. just remember, the more you do to you plants the less likely they'll be similar to wild. I'm of the school that you plant it and leave it alone. no pesticide, nothing. maybe pull up a few of the bigger weeds but nothing more.