Hi, Achik, and welcome to the forum. There is at least one other cheese-maker here from Malaysia - KazAugustin is her screen name.
My understanding may be backwards, but ... I think thermo cultures are dominant in most yoghurts. Cultured buttermilk, by contrast, features mostly mesophilic cultures. So yes, using yoghurt is certainly a way to make mozzarella.
I would recommend NOT try to combine cultures (yoghurt) + citric acid. The whole point of using cultures is to let the cultures develop acidity as they multiply. This gives you a chance to test the readiness of the curd for the ideal pH for stretching - either using a pH meter, or just taking a little of the curd and trying it in hot water to see if it is at the right stage.
Citric acid, by contrast, is all-or-nothing -- you are simply pushing the pH down immediately, and if you miss the ideal pH "window," then it is too bad, so sad.
I suppose in theory you could increase the acidity a bit with a small amount of citric acid, and then let the cultures take it the rest of the way ... but why? You lose the benefit of the extra flavor imparted by the development of the cultures, and you gain very little except maybe a little less time.
Now, with all of that said ... give some thought to trying out other cheeses besides mozzarella. Moz is widely featured as a cheese for beginners, but in fact, based on both personal experience and countless posts on this forum, even experienced cheesemakers find it to be quite challenging to get it right. The only reason I can think of that it is pushed as a beginner's cheese is that 1) it is possible to avoid using cultures, using citric acid instead, and 2) it does not require a press. But with regard to #1, you still have to use rennet, and that's a lot harder than finding cultures (since you can use yoghurt or buttermilk in addition to the freeze-dried cultures). And, in my experience, it is quite challenging to get just the right amount of citric acid, and it tends to make the milk curdle (not form curds, but curdle) before you can even add the rennet.