BANGKOK—Aung San Suu Kyi, the civilian leader of Burma (also known as Myanmar) who was ousted in a de facto coup this year, was convicted on two charges Monday and handed a four-year sentence that was quickly cut in half—in proceedings widely criticized as a further effort by the country’s military rulers to roll back the democratic gains of recent years. They serve to cement a dramatic reversal of fortunes for the Nobel Peace laureate, who spent 15 years under house arrest for resisting the Southeast Asian nation’s generals but then agreed to work alongside them when they promised to usher in democratic rule. Monday’s verdict was the first in a series of cases brought against 76-year-old Suu Kyi since her arrest on Feb. 1, the day the army seized power and prevented her National League for Democracy party starting a second term in office. If found guilty of all …