There are several things to consider when outsourcing software development to Vietnam:
Communication: Make sure that you have clear and consistent communication with your development team, as language and cultural barriers can sometimes be an issue.
Project management: Ensure that you have a clear project plan and that the team is following it. Monitor progress regularly and make sure that the team is meeting deadlines.
Quality: Make sure that the team is delivering high-quality code and testing it thoroughly. It's also a good idea to have a code review process in place.
Legal issues: Make sure that you understand the local laws and regulations and that your contracts are in compliance. It's also a good idea to work with a reputable local law firm.
Cultural differences: Be aware of cultural differences and try to be sensitive to them. For example, punctuality may not be as important in Vietnam as it is in some Western countries.
Overall, the key is to establish clear communication and expectations, have a solid project plan in place, and work with a reputable team that you can trust.