You may need an embassy visa for Taiwan if you have a Vietnamese passport

Travelers may be eligible to apply for travel authorization to visit Taiwan for Business or Tourism for a maximum stay of 14 days. Travelers can apply for a Travel Authorization Certificate only if they hold a valid visa or residence permit or a visa or residence permit issued in the past 10 years by Australia, Canada, New Zealand, a European Union country, a Schengen country, United Kingdom, or United States. Travelers can submit the eTA application online. Once the application is approved, travelers receive their eTA confirmation electronically. Approved eTA is valid for 90 days. Multiple entries within these 90 days are allowed. A valid eTA is required to board the flight. If the eTA is expired or doesn’t match the traveler’s passport information, travelers will not be able to board their flight. Please see the source for more details on the Travel Authorization Certificate.

Travelers need a visa to visit Taiwan for Business or Tourism. Travelers can apply for an eVisa if they are traveling to Taiwan in a tourist group designated by the Tourism Bureau of the Ministry of Transport. A Taiwan eVisa is the fastest and easiest way of obtaining a visa for Taiwan because travelers can submit their applications and supporting documents online. Once the application is approved, travelers receive their eVisa confirmation electronically. Travelers who want to visit Taiwan but are not eligible for an eVisa must fill in a form under General Visa Applications on the Bureau of Consular Affairs website and submit it to the nearest Taiwan embassy.