In this study, a comparative analysis was conducted on the onomatopoeias of the Korean and the Thai. The results show that Korean onomatopoeias have the most plosives, followed by affricates, and fricatives, and have extremely few nasals or assonants. Also, usual sounds and tense sounds are many and strong sounds are relatively few. The Thai language also has the most plosives, followed by fricatives, and relatively few affricates and assonants. However, Thai language was found to have far more tense sounds than strong sounds. In the distribution of onomatopoeias of the Korean language, there are many onomatopoeias with two syllables and four syllables, whereas the Thai language have the most onomatopoeias with one syllable. It appears to be because the pure Thai is a single syllable language made up of one syllable. When onomatopoeias are classified according to the object that makes sound, the two languages all have the most sounds made by things, followed by the sounds made by humans, but the sounds made by animals or nature are relatively very few. In the case of the Korean, the prefix consonants are classified into usual sounds, tense sounds, and strong sonds, and through these sounds, strong and weak nuances are expressed, and more diverse nuaces can be expressed acoording to consonant repalacement. Also, through final consonants, diverse nuance expressions according to the kinds of consonants can be made. Vowels are also classified into positive vowels and negative vowels, and through the vowel replacement, diverse nuances such as big and small, strong and weak, heavy and light, wide and anarrow can be expressed. In the case of the Thai, different nuances according to the properties of consonants can be expressed, and in the case of vowels, nuance expressions such as big and small, heavy and light can be expressed through vowel replacement in the dialects of some regions.