My (terrible) experiences not only in Thailand, but also Sri Lanka etc., have now taught me, that in third world countries, ONLY deal with Governments agencies (especially customs) with an agent involved!
They are literally magicians, they can even let you know how much you have to pay, before the goods arrive, LOL!
Otherwise, you may be stuck with severe headaches, heartaches, and a <deleted>load of wasted time and effort, all amounting to absolutely nothing, and in the end, have it all sorted out in minutes by an agent.