The word Cham (usually with a capital) is an archaic, and erroneous, spelling of the Turkish word usually given nowadays as Khan, which is also a word in Persian. Arabic, Urdu and such languages. Both Cham and Khan are pronounced with a hard 'k-' sound in first place; the vowel is given in OED as that in 'cat' and 'that' (IPA: /kæn/), although khan is also given with the sound of 'can't (IPA: /kɑːn/). (Don't ever pronounce 'Cham' like 'sham', or the first syllable of 'champagne' (IPA: /
ʃæm/.) In any case, the 'kh-' at the beginning of the word in its (original) central Asian languages is pronounced as an unvoiced velar or uvular fricative, IPA: /χ/.
Cham, like khan, was the title adopted by rulers in Asia, most famously Genghis (or Chingis) Khan. It was a title inherited by his successors; it also become one of the titles of the Chinese emperors. Now it is a title of various rulers, and more or less petty officials 'ruling' over small districts. It is also a surname, quite common in Pakistan and neighbouring countries. Since the sixteenth century, it has been mostly used figuratively, in reference to 'great men', or men who believe themselves great, in cultures other than the Islamic world from which the word comes.