The father of a missing Auburn University student is "worried sick" about his son, who vanished without a trace on a study abroad program in Asia.

Paul Harrie told FOX News Wednesday that he can't imagine where his typically reliable son Michael Griffin Harrie, 29, could be or why the family has heard nothing from him in weeks.

The veterinary student was last seen July 14 in Thailand doing some sightseeing.

Harrie was supposed to meet his parents two days later back in Japan, where he'd been studying at Iwate University in Morioka.

But he never arrived, and the family has had no word.

"We're sort of worried sick about him," Paul Harrie said on FOX. "He's very responsible. He always communicates with us. We just don't know."

Michael Harrie, a California native, began his excursion to Bangkok on July 7. He was reported missing two days after the last reported sighting.

Security cameras at the airport in Bangkok show Harrie heading alone toward the airport's exit, Mike Clardy, Auburn's director of communications, told FOXNews.com on Tuesday.

Clardy said authorities do not suspect foul play and are treating it as a missing person case.

Anyone with information should call the university's security office at (334) 844-8888.

FOXNews.com's Michelle Maskaly and The Associated Press contributed to this report.