I (heart) Khao San Road. It's a wonderful choice for anyone who is vegan/vegetarian with friends who eat meat has they have a great selection for both. They also recently created a separate vegan/vegetarian menu!
The MUST TRY for a vegan or vegetarian would be the Gaeng Massaman curry. Please note it's not on their vegan menu but the server asked if I wanted it vegan so I guess it's possible - and It's to die for. It's very filling but if you're super hungry I suggest splitting the garlic tofu nuggets to start. To drink, if you order coconut water it comes in a giant glass!
I also tried the yellow curry for takeout lunch, the portion size is much smaller than dinner or maybe in this rare case my eyes were smaller than my stomach - or maybe it was just the takeout containers. It also didn't beat out the Gaeng Massaman for taste.
Atmosphere is super chill, great to go with friends, parents, or a date. I went on St. pattys and the owner came around and chatted with us for a bit, he was very friendly :)
Go before 6:30pm if you don't want to wait an hour for a table! And don't call them when you're hung over on a Saturday morning as they sadly don't do delivery :(