Clearly the Capital of a country should be listed like for any other country whether it has the largest population or not. The argument of population is only valid for other cities being listed in case of countries with more than one time zone. As regards the spelling one could argue whether it should be the spelling in Vietnamese language "Ha Noi" or the spelling in English language "Hanoi". For the English language interface I would suggest that "Hanoi" is more appropriate.
Clearly the Capital of a country should be listed like for any other country whether it has the largest population or not. The argument of population is only valid for other cities being listed in case of countries with more than one time zone. As regards the spelling one could argue whether it should be the spelling in Vietnamese language "Ha Noi" or the spelling in English language "Hanoi". For the English language interface I would suggest that "Hanoi" is more appropriate.