Five separate protests in Phnom Penh came to a crescendo Sunday in front of Prime Minister Hun Sen’s office building—the Peace Palace—with an estimated 50,000 protesters marching down Russian Boulevard and calling for the long-serving CPP leader to step down. Now in their 15th straight day, the opposition CNRP’s demonstrations calling for fresh elections and the prime minister’s resignation have grown in strength this week, with Sunday’s march amounting to the largest protest against Mr. Hun Sen’s government in at least 15 years.