KUALA LUMPUR, Malaysia—A positive COVID-19 test among U.S. Secretary of State Blinken’s traveling party has cut short the top diplomat’s first official tour of Southeast Asia. A member of the press corps accompanying Blinken on what was to have been a three-nation visit to Indonesia, Malaysia, and Thailand tested positive for the coronavirus on Wednesday in Kuala Lumpur, forcing Blinken to abandon the program at his next and last stop in Bangkok, and return to the United States. Instead of spending Wednesday night in Bangkok, the State Department said Blinken would fly to the Thai capital for a very brief logistical layover before traveling to Guam to refuel and then continuing on to Hawaii. The abrupt change in plan was caused in part by fears that others in the delegation might also test positive, requiring them to quarantine in Thailand over the Christmas holiday. The journalist who tested positive will …