Thining or Thinning: How To spell?
The word Thining is misspelled against Thinning, which is present continuous of "Thin"
Thinning has double "nn" is mispronounced as "n"Remember double 'NN' in between the strings thi & ing which should not be misspelled with single 'N'
Wrong Spelling:  thi-n-ing  Correct Spelling:  thi-nn-ing 
Find more wrongly spelled words of Thinning to spell it well.