Thesm or Theism: How To spell?

The word Thesm is misspelled against Theism, meaning "Belief in God."

Word contains consecutive vowels 'EI' in between alphabets th & sm is misspelled as 'E' as letter 'I' is phonetically ignored
Wrong Spelling:  th-e-sm 
Correct Spelling:  th-ei-sm 
Explore spell check of Theism to spell without errors.