From Saigon, you can take a bus all the way up the coast. I recommend doing a Mekong Delta tour from Saigon, and after that, head north to Hoi An and Hue. A lot of people like Nha Trang, but I wasn't a big fan. I'm not sure how to get to Laos from Hanoi, but you can take a bus from Hue to Savannakhet in Laos if you don't make it as far north as Hanoi. Have fun!