"What month is it?" would be a more colloquial/natural way to say this.
Or "What month is this?"
Which month is it?
The differences in question here are inflectional differences for different expressions. "What month is this?" Is, yes, probably most common in English. "This is what month?" Also turns up for a certain sort of emphasis.
Excellent observation. I was about to say the same thing.
Is there another way to phrase the Indonesian btw?
"Apa yang bulan ini?" Does that work?
It sounds suspicious. What month is this month?