Thai Foreign Minister Sompong Amornwiwat was believed to have been stranded in Germany on Thursday after demonstrators invaded both of Bangkok's airports, forcing a cancellation of flights, according to dpa. Flights from Europe to Bangkok by Thai Airways International and other airlines were cancelled as a result. Bangkok aviation authorities agreed on Thursday to open the U-Tapao Air Force Base as an alternative. Sompong's presence in Germany could not be confirmed, since he was not visiting the country as an official guest. It was understood that he was resuming his interrupted trip home after the air base near Bangkok was opened as an alternative destination for some scheduled flights, but no official confirmation about his movements was available. Sompong has been working to prepare for a summit of the Association of South-East Asian Nations (ASEAN) in Chiang Mai, Thailand from December 15 to 17. The 10 ASEAN nations and leaders of China, Japan and South Korea are set to attend.