Pronouncing this final 's' is difficult for Indonesians and for some reason embarrassing, rather like when English people attempt to pronounce the French 'r'.
But if you want to communicate well, and if you want a good score for pronunciation in IELTS speaking, then you had better start producing the 's' at word endings!
In this video, former student George does his best to put 's' in all the right places. I've added a scoring feature to help you follow his 'performance'!
A good way to practice 's' is to record yourself, and then listen back following a tapescript. Focus on the 's' in particular. Exaggerate it. Make it longer and louder. In the IELTS test make sure the examiner can hear it!