Resolved questions
Used or not used?

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