Addition กฎ [กด-ghod] and กฏ [กด-ghod] They came from Pali-Sanskrit words. They are same pronunciation but 1.กฎ[dor cha da] means law. You can use กฎหมาย[ghod-mhai] = law , กฎธรรมชาติ[ghod-tham-ma-chad] = law of nature , กฎแห่งกรรม = law of action,reciprocal deeds etc. [dor-cha-da]Some words that we often use like ทฤษฎี[trid-sa-dee] = theory , มงกุฎ[mong-khud] = crown,tiara , ศาลฎีกา[sarn-dee-ga] = supreme court {ศาล[sarn] = court} 2.You can use กฏ[Dor pa dak] when It follow the word ปรา[prar] ex. ปรากฏ[prar-ghod] = appear , ปรากฏการณ์[prar-ghod-gan] = phenomenon and there are many words that use ฏ[Dor pa dak] ex.ปฏิบัติ[pa-Di-bud] = act,practice , ปฏิกิริยา[pa-Di-gi-ri-ya] = reaction etc. [Dor-pa-tak]Some words that we often use like กุฏิ[gu-Di] = cloister , ปาฏิหารย์[pa-Di-harn] = miracle , ปฏิเสธ[pa-Di-sed] = reject , นาฏศิลป์[nard-Da-sin] = dancing art etc. 3.The alphabet ฅ[kor-kon] according to the royal institute,we do not use this alphabet in nowaday but you can see in some places like the name of the TV show - คนค้นฅน 4.The alphabet ฃ[khor-khuad] - the same sound of ข[khor-khai] according to the royal institute,we do not use this alphabet in nowaday. P.S. I searched some information from the internet because many people usually use some words by mistake even Thai people