Thir or Their: How To spell?

The word Thir is misspelled against Their, a pronoun meaning "The possessive case of the personal pronoun they; as, their houses; their country."

Word contains consecutive vowels 'EI' in between alphabets th & r is misspelled as 'I' as letter 'E' is phonetically ignored
Wrong Spelling:  th-i-r 
Correct Spelling:  th-ei-r 
Find more wrongly spelled words of Their to spell it well.