Pronunciation: [ˌʌndəpˈe͡ɪn] (IPA)
Correct spelling for the English word "underpain" is [ˌʌndəpˈe͡ɪn], [ˌʌndəpˈeɪn], [ˌʌ_n_d_ə_p_ˈeɪ_n] (IPA phonetic alphabet).