Thanks for your concern,
base on your Schedule single entry is enough. for Nha Trang and second day Ho Chi Minh
Vietnam offers 15-day visa exemptions with single entry for visitors from the U.K.. However, their
passports should have at least six months of validity upon the date of arrival to meet airlines’
requirements, and their arrival date is NOT within 30 days from their last exit date with visa exemption.
Otherwise, they will need a Vietnam visa.
If you stay more than 15 days please apply for Vietnam visa
Stepfanno Tran (Mr. )