Now they have to attach their original bank passbooks with their visa applications instead of photocopies or bank statements to prove they have savings of at least $5,000. The money must have been in the account for at least one month at the time of submission.

Tour operators recommend that tourists should also enclose a copy of their labor contract, the original leave permission letter or business license to improve the chance of approval.

South Korea has waived fees for C-3 short-term visit visas for all ASEAN member countries from October 1 to December 31.

More than 450,000 Vietnamese visited South Korea last year, up 40 percent from the previous year, making Vietnam the seventh largest source market, according to the Korea Tourism Organization.

However, a number of Vietnamese tourists reportedly left their tours and illegally stayed in South Korea in recent years. In 2016, a total of 163 Vietnamese people visited Jeju Island in South Korea as tourists. 59 of them disappeared from their hotel in Jeju. Many of them then managed to find jobs with the help of other Vietnamese people living in South Korea.

Vietnam is the third leading tourism destination for South Koreans after Japan and mainland China, with the number of visitors expected to increase by 30 percent this year to four million, according to the Global Destination Cities Index published in July by Mastercard.

Last year, more than 3.4 million South Koreans visited Vietnam, a 44 percent rise year-on-year, accounting for 22 percent of all international arrivals, according to the Vietnam National Administration of Tourism.

In the first nine months of this year, Vietnam welcomed 3.1 million South Koreans, up 22.5 percent year-on-year.