The players had completed a training course in Spain with three friendly games against hosts Spain, Japan and a Spanish side there.
With the suspension of the domestic futsal tournament due to COVID-19, international friendlies gave chief coach Pham Minh Giang the chance to review positions of the squad for big games ahead.
Captain Tran Van Vu told fifa.com that all the players are in good form, aiming to cruise into Round 1/8 as they did five years ago.
While in Lithuania, Vietnam will play another friendly game against Morocco on September 6 before beginning their quest at the World Cup 2021.
According to an earlier draw, Vietnam are in Group D alongside world defending champions Brazil, the Czech Republic and Panama.
They are scheduled to take on Brazil on September 13, Panama on September 17 and the Czech Republic two days later.
This is the second time Vietnam have competed in the FIFA Futsal World Cup. In their first global competition in Colombia five years ago, Vietnam made history after storming into Round 1/8.