Thest or Theist: How To spell?

The word Thest is misspelled against Theist, a noun meaning "One who believes in the existence of a God; especially, one who believes in a personal God; -- opposed to atheist."

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