Right to left or left to right does not matter.
A spell checker must match
- the language
- the alphabet (some languages can be written in two alphabets)
- the orthographical rule set (e.g. there are two orthographies for Norwegian)
Since all your examples use an extended arab alphabet (and have oly one orthography, don't they?), things should not be so complicated.
I googled for "spell checker urdu" and found
Urdu Spell Checker Utility
I hope you can do so with the other examples.
Oh yes, the encoding could be an issue: whenever you call some functions of the spell checker, make sure that the encoding of your data and the encoding expected by the spell checker do match!