A common advice when you learn a foreign language is to speak with native speakers to improve your speaking skill. Unfortunately, most of the times, you won’t have many face-to-face time with native speakers. Plus speaking with native speakers can be embarrassing, inefficient (if you’re trying to converse and not just train your speaking skill), and costly (some people do pay to speak with native speaker, which is reasonable: if a foreigner tries to practice his Indonesian with me, I’ll probably charge a fee, too).
But, what if you can just practice your speaking skill alone? Well, it is possible by doing a simple thing that we always do: thinking.
When you think, notice that your thoughts will be encoded most of the time in your native language. If you can shift to thinking using a foreign language, then you can have some free, convenient practice time. At first, you will have to do this deliberately, but with time, you may even caught yourself thinking naturally in your target foreign language. And once, you are able to think naturally in another language, speaking will just be a matter of moving your muscles in the right way to produce the desired sounds that you hear inside your head.
One disadvantage of using this method is having the wrong pronunciation. If you have the wrong pronunciation of a word in your head, nobody will correct it. And this wrong pronunciation when thinking will translate into wrong pronunciation while speaking. But, then again, native speakers won’t correct you either if you make mistakes unless you make it clear that you won’t be offended by their correction (and even then, the people who’ll correct you will probably be just your teacher that you pay, not some acquaintance that doesn’t really bother). This is easily solved by checking the pronunciation of every word you encounter (using a text-to-speech app or a dictionary that supports International Phonetic Alphabet) and immerse yourself with listening materials of your foreign target language.
I use this method and it works pretty well. At the very least, I’m equally capable of speaking English as fluently as my rich friend that paid quite a sum of money for a native English teacher. I’ve checked my pronunciation with some native speakers and they say that it’s acceptable (I have a clear enough American accent sprinkled with a somewhat black vernacular ghetto accent that I accidentally gain from listening to a lot of hip hop music).