For me, the commas are correct.
I am still planning to go to Malaysia, but as for the exact dates, I don't have them yet, since I want a bit of flexibility with my schedule
Should there be commas before I don't and after yet?
I wouldn't have put a comma between "Malaysia" and "but". In my opinion, the one between "yet" and "since" is optional.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.
It's more important to put a full stop (period) at the end.