Cucumber or 'tangua' is called for most fresh vegetable side dish accompanying hot dishes.
In the U.S., there are 3 types of cucumber, English cucumber, regular cucumber, and pickling cucumber. English cucumbers are dark green and has soft seeds while regular cucumbers are dark green with yellow stripes and may have hard, white seeds. Pickling cucumbers are light green with white or yellow stripes and used for pickling but available fresh.
In Thailand, only pickling cucumbers are available. They are smaller and very crunchy.
For all Thai cooking, I find that there are no difference with any of the available U.S. cucumbers.