Altho or tho is not accepted in formal English writing. It is better to keep to although and though.
Altho atau tho tidak diterima dalam formal English. Lebih baik gunakan although dan though untuk penulisan sekolah, reports, kerja pejabat dan sebagainya.
Of course you can use it when you are babbling on tweeter, fb, everyone will understand!
Although means something that seems to contradict, but, however.