The phone number from Vietnam did not receive the message even the message has sent successfully from SNS

Please be advised that when sending SMS messages to Vietnam using Amazon SNS, you are required to use a registered sender ID as your origination identity in order to ensure deliverability, as per the requirements mentioned here.

If you do not have a registered sender ID for Vietnam, which is most likely why you are experiencing delivery issues to Vietnam destination numbers. To ensure deliverability, I recommend that you register a Sender ID to send SMS messages to Vietnam destinations, by following the steps mentioned here, this will require you to open a separate Service limit increase case to register the sender ID.