Vientiane is an easy and affordable destination. You can catch a flight in about an hour. Submit your documents at the embassy on Monday and pick them up on Wednesday at the earliest. Take a taxi directly to the Friendship Bridge, where you can hire a private driver to take you across and drive you to Udon Thani, a 45-minute trip. This is also a way to do a border bounce without getting an actual visa. From Udon Thani, you can catch the 3:15 PM flight to Bangkok with VietJet. Booking online through their app costs between 800-1200 baht, whereas booking in person can cost around 3000 baht. Now you're back in Bangkok.