What is the difference between a registered trademark and unregistered trademark?
Each country allocates a level of respect to unregistered Trademarks. This varies from very little to serious as in the USA.
In the UK if you have an unregistered Trademark you are likely to be allowed to continue use in the area where you have established goodwill. Example you have a restaurant in Bristol and your regular customers come from a twenty mile radius. However someone has obtained a registered UK Trademark for a similar or identical Trademark covering restaurant services. The owner of the registration is going to be able to prevent you opening another restaurant with the same name outside your Bristol plus twenty mile area, unless you can persuade the tribunal to cancel the registered Trademark. This is most unlikely unless you can show good evidence of custom beyond Bristol.
A registered Trademark gives you the right to use the letter R encircled next to your Trademark and will carry a legal presumption that the Trademark is yours for the country in question. You will also find that intellectual property insurance is more cost effectively obtained. Additionally the authorities such as police and customs may possibly assist in preventing misuse of your Registration.
Source: Quora
It is wise to consult the advice of a IP attorneys in Vietnam to help assist you with your trademark. We are a legal marketplace with quality lawyers who are knowledgeable in various areas of the law—including intellectual property rights.