Pronunciation: [t͡ʃˈe͡ɪnəst] (IPA)
Correct spelling for the English word "chainest" is [t͡ʃˈe͡ɪnəst], [tʃˈeɪnəst], [tʃ_ˈeɪ_n_ə_s_t] (IPA phonetic alphabet).
Correct spelling for chainest