According to the law of Vietnam, foreign citizens shall report to the local public security authorities within 12 or 24 hours (remote areas) after they enter Vietnam. If changing residence during your stay in Vietnam, you shall report to the public security authorities of your current place of residence. Upon entry, the Vietnamese exit and entry administration department will state the period of stay according to the validity of the visa, and the maximum period of stay of the tourist visa is 30 days. If staying for a long time, you should apply for a residence certificate corresponding to the visa according to the regulations. If your residence is due, the receiving department or relevant personnel should apply to the Ministry of Foreign Affairs or the exit and entry administration of the Ministry of Public Security for an extension of stay. According to the nationality law of Vietnam, dual nationality is not recognized by the Vietnamese government. If a citizen of another country joins Vietnamese nationality, he or she shall withdraw from the original nationality first. And if a Vietnamese citizen joins other nationality, he or she will also lose the Vietnamese nationality.