Bangkok Immigration: Red Light Mystery Solved!

My recent trips through Bangkok's Suvarnabhumi Airport left me with a perplexing experience.  Twice, upon exiting Thai immigration, my passport and fingerprints were scanned, a red light illuminated, and I was briefly detained for secondary screening.  This happened despite uneventful immigration processes in Kuala Lumpur and the United States following the issuance of my DTV visa.  What triggers this secondary inspection?  Many travelers wonder about similar experiences, especially those on long-term visas.  Common reasons for secondary checks can include discrepancies in passport information, potential visa violations, or even a random selection process.  It's crucial to ensure your visa is valid and your travel documents are accurate to minimize these delays.  Experts advise maintaining meticulous travel records and packing any necessary supporting documents, such as flight itineraries and visa confirmations.  While this random secondary screening can be unnerving, it's generally not cause for serious concern.  However, for peace of mind, it's always best to be thoroughly prepared before international travel. Have you had a similar experience at Bangkok's immigration? Share your thoughts and experiences in the comments below!