The spelling of the word "LESING" can be explained using the International Phonetic Alphabet (IPA). The sound of "LESING" is represented by the phonemes /l/, /ɛ/, /s/, /ɪ/, and /ŋ/. The first sound is the voiceless alveolar lateral fricative /l/, followed by the open-mid front unrounded vowel /ɛ/. The third sound is the voiceless alveolar sibilant /s/, followed by the close front unrounded vowel /ɪ/. The final sound is the velar nasal /ŋ/. The correct spelling of this word is "LEASING," which refers to the contract of renting an asset for a specified period.