@Nami *******
understand that those at the embassies, and at immigration profile, and stereotype. If you fall into these profiles they will pay special attention to you, and mostly when you try to enter the country, not at the embassy. You can be issued a visa by the embassy, and still be refused entry if you fit certain profiles. A nice haircut, and dressed in nice clean clothes, without carrying a backpack, only a suitcase, is your best look. The school gave you what you need. Don't stress about that. Just make sure you make an appointment online for the Vientiane embassy, as they don't allow walk-ins anymore.