SEOUL—Unionized workers of Samsung Electronics have threatened what would be an unprecedented strike at the tech giant if their demands for higher pay and better working conditions are not met. Union representatives held a rally on Wednesday near Samsung’s headquarters in midtown Seoul after government arbitration broke down earlier this week. They are calling for wage gaps among employees to be narrowed, more paid leave, and better health benefits. “There are many options, one of which is a strike,” said Kim Hang-yeol, head of one of the four unions representing Samsung Electronics workers. “We will continue to fight to ensure wage negotiations and collective bargaining with not only Samsung Electronics, but also all unions of Samsung affiliates.” Union officials sought a direct meeting with the top management of the sprawling conglomerate’s flagship chipmaker and world’s top smartphone manufacturer. The potential impact on the company’s operations is not clear as the …