BANGKOK—A series of coronavirus outbreaks in Thai factories is raising concerns that the export sector could be hit hard, threatening to further undermine an economy as it struggles to recover from the lockdowns’ crippling blow to the crucial tourism industry. The virus has swept through over 130 factories, including those supplying international brands, with more than 7,100 cases across 11 provinces, making manufacturing one of the top sources of infections along with prisons and construction camps. The affected plants are just a fraction of about 63,000 factories in Thailand that employ 3.4 million, government data show, but officials worry about the impact on exports that have kept the struggling economy moving as income from tourism has collapsed. In 2020, exports accounted for 45 percent of gross domestic product. The tourism-reliant economy, a global trade hub, suffered a steep 6.1 percent contraction last year, and last month the government trimmed GDP …