This is a type of amulet from Thailand called a PALATKIK.  Such amulets are made by a handful of Buddhist monks with the ancient arcane knowledge and rituals necessary to make powerful magical amulets.  They are usually cast in bronze at temple foundries, but some are hand-carved from wood, bone or horn.  They are provided to parishioners who request them personally and make a donation.  One does not usually see them worn openly such as with other temple-consecrated amulets.  They are kept inside the shirt on a necklace or often on a keychain inside the pant's pocket.  This type of amulet predates the introduction of Buddhism in Thailand, but the beliefs in them did not get phased out with Buddhism, but incorporated as Buddhism is very tolerant of diverse beliefs.  The amulets are believed to bring multiple positive benefits to the bearer.  These include assistance in matters of performance, finding the right partner, maintaining faithfulness or fidelity of a partner and also protection from misfortune, such as danger, accident or illness.