carbs are tough to avoid here since as you said, almost everything involves rice or noodles. However, there are a ton of "snacks on a stick" available all over the place where it is basically just meat prepared a number of delicious ways.

There is a type of food called Isaan food (sometimes spelled Esaan) which is basically the cuisine of the north-east of the country. Almost all of this comes without rice as the rice aspect is "sticky rice" which is served on the side. I normally just skip the rice altogether if i am trying to avoid carbs. The most famous Isaan dish is papaya salad or "som-tum" and although a tiny bit of sugar is used in the process, this is only a small amount.

Virtually all of the delicious curries can be eaten without the rice or it's up to you how much of it you use. I don't think you will have as much of a problem as you might be thinking. It is just a bit more expensive (still cheap) to eat this way.

Careful of most Thai beverages as it is extremely common for a LOT of processed sugar to be added in the form of what the thais simply call "syrup" (it's just melted sugar)

Mainly i think snacks on a stick are going to be your "go to" there are lots of them and they are available pretty much everywhere, especially in BKK.