Save the elephantsCan I save the elephants without adding the s? Can Students from Thailand be called the stud?

You can do it without adding s. Because the word after the specifically refers to the thing mentioned above, if s is added to the thing mentioned above, s will also be added to the thing below; otherwise, s will not be added. If we simply translate "save elephants", it should be save elephants, because it does not refer to a specific elephant.

As mentioned above, because the following thing refers specifically to the thing mentioned above, if s is added to the thing above, then s will also be added to the following; otherwise, no s will be added. Students from Thailand is best translated as "Students from Thailand".