Choosing a web vendor in a market you did not grow up in is mostly a due-diligence problem. The technology is rarely the risk; the working relationship is. These five questions surface most of it in a single meeting.
1. Who will I speak to every week, and in what language?
Sales meetings are often in fluent English while delivery happens in Vietnamese. Ask to meet the person who will actually run your project and confirm the working language for status updates and written specifications. If specs will be in Vietnamese, agree now who translates them and who signs off.
2. Whose name is on the domain and the hosting account?
Both should be registered to your company, with your company email as the administrative contact. This is standard practice and any reputable vendor will agree immediately. Hesitation here tells you a great deal.
3. What exactly is in the contract, and in which language?
For a foreign-invested company, a bilingual contract with a stated governing version avoids painful ambiguity later. Make sure scope, payment milestones, acceptance criteria, and intellectual property assignment are all written down — verbal agreement is common practice locally, but it will not help you at handover.
4. What does support cover after launch?
Separate bug fixes from new features explicitly, with a defined warranty period and a response time. Ask what happens outside business hours, and whether support is included or billed hourly in year two.
5. Can I see how you work, not just finished screenshots?
Any portfolio shot looks good. Ask to see a project in progress: how requirements are captured, what the code looks like, who tests before launch. Then give them a real scenario — the site goes down on a Saturday night — and judge how specific the answer is. Vague reassurance is the answer you are screening for.