Upvote:2
Hi you may have a problem.
We work with lots of travellers and VN has specific rule about being a dumping ground for used equipment. You can quite possibly be made to pay the duty on the equipment you intend to leave. It is better to say it is for training purposes and will be leaving the country with you. If you show your 'letter' you will prove that you do not intend to take it with you...so duty is payable. Despite your good intentions the next 100 people will sell the stuff on the street. They will consider you a smuggler... albeit one who is upfront with 'proof'.
You can just have the letter adjusted and only produce it under duress. If you are on a government sanctioned trip (eg local peoples committee approved) the letter of invite from the peoples committee works wonders at customs.