Apple does not respond to posts made in these forums. The only reply you will get are from fellow users. Since you provide no details about your issue, I can only direct you to one of a number of threads regarding problems connecting to the iTunes Store and suggestions offered in many of them. I'd suggest you take a look at some of those threads - look under "More Like This" at the right - and you may find something that will help you.
As to your second question, you cannot install any new fonts on your iPad. The languages supported in the iPad are listed here:
You may find an app that would support Khmer within that app if you search the App Store.
Finally, it's usually not a good strategy to mark your own followup question as "solving" your issue. People will see that your question has apparently been solved and ignore it for that reason.