I am currently living in Bangkok and I love astronomy. However, I haven't been able to find an official astronomy exam that I can do to gain college credit. Could someone help me out please?
There is a Dantes Standardized Subjet Test (DSST) in astronomy. I have no idea if and how widely colleges give credit for these exams. Typically, you will start with physics and choose to specialize in astronomy. Therefore, most standardized exams are for physics which may have a handful of astronomy questions.
There is a GCSE in astronomy offered by Edexcel: http://www.igcse2009.com/gcseother/gcse-astronomy/
The assessment has two parts, an exam, and a series of two observation task (aided and unaided).
The course is suitable for 14-16-year-olds.