Acknowledgements
The authors are very grateful to the Thailand Research Fund for funding support to this research No.RDG5150076. Our thanks go to Mr. Somchai Pornchaivivat in guiding the route of transporta- tion, the LSPs in Thailand and Vietnam and TBA (Vietnam) for inquiries about transportation routes, costs and time, and experts for identification and assessment risk of routes, whose names unfortunately cannot be revealed because of confidentiality agreements. The authors are very appreciative to all of the anonymous reviewers for their valuable comments.