Very close to Hot Springs you will find Lake Ouachita, Lake Cathrine and Lake Degray. All have beautiful camping spots and will handle your 30 footer with no problem. They are anywhere from 5 to 30 miles from Hot Springs.
Crater of Diamonds state park near Murfreesboro, Arkansas is a very nice place and as already said, you can dig diamonds and keep them as well as other semi precious stones that you find. There is a small fee to do the digging.
Crater of Diamonds state park is about 60 miles from Hot Springs.
Hope this helps.
