2 of the most important Thai Words you should learn immediately are Hong Nam.
Hong Nam is Toilet.(ห้องน้ำ)
The reason is many westerners first arriving in Thailand will not be use to the spiciness of Thai food or the high bacteria levels in the food. This will cause you some stomach mis-comfort guaranteed.
Best to always understand where is the closest toilet to where you are eating!
There are 2 types of toilets, western sit down toilets and Thai squatting toilets.
The Thai squatting toilets are usually filthy.
Be advised you will NOT find any toilet paper, so best to bring your own. Cleaning your bottom Thai style with water with nothing to dry is very uncomfortable.
The western sit down toilets, depending on location may be a much better option if available.