I also have a ring with stamped with STS and 14k

Answer 1

STS is a jewelry company, so that's the maker's mark.  14K means it's 58.5% gold, unless it's followed by GP, HGE, GEP, or something similar.  Thailand is a large supplier of gemstones and jewelry, so that usually indicates that the stones are geniune.  It sounds like a good ring.