Sea Ltd. swung back to a loss in the third quarter, hit by flagging consumption and intensifying competition from Alibaba and TikTok on its home turf.

The stock fell 13% in early New York trading — the biggest intraday decline in three months — after the company posted a net loss of $149 million, compared with a profit of $322 million the previous quarter. Southeast Asia’s largest internet firm reported a 4.9% rise in sales from a year earlier to $3.3 billion, versus the average estimate of $3.2 billion.