Congrats! My family is from the region, so I'll try to give you some answers
There is the typical Thai fare, Pad Thai, Lad Na, Pad See Ew. But in the Issan they eat a lot of papaya salad (som tam), grilled chicken, and sticky rice. You can avoid carbs, but it's going to be pretty difficult because rice usually comes with everything.
Larb (meat salad) is good, maybe trace carbs from the toasted rice but it's just meat with herbs. They will make it with most types of meat (beef, duck, fish) so you have variety. Grilled chicken is the most popular thing, so that is an option.