Where does “คริสตธรรม” come from?

คริสตธรรม (Thai) comes from Thai ธรรม, from Sanskrit धर्म, from Proto-Indo-Iranian dʰármas, from Proto-Indo-European dʰer- — to support; to hold.

Ancestry of “คริสตธรรม”, step by step

Step	Language	Word	Meaning
1	Thai	ธรรม	dharma; doctrine
2	Sanskrit	धर्म	morality, virtue, moral code, good deed, good...
3	Proto-Indo-Iranian	dʰármas	—
4	Proto-Indo-European	dʰer-	to support; to hold

คริสตธรรม — Etymology, Origin & Word History | Etymology Explorer