Where does “บาป” come from?

บาป (Thai) comes from Pali pāpa, from Sanskrit पाप, from Proto-Indo-Iranian pāpás — bad.

บาป (Thai): sin; badness; evilness; bad; evil

Definitions

Step	Language	Word	Meaning
1	Pali	pāpa	evil, sinful; a sin, bad deed
2	Sanskrit	पाप	bad, vicious, wicked, evil, wretched, vile, low;...
3	Proto-Indo-Iranian	pāpás	bad

บาป — Etymology, Origin & Word History | Etymology Explorer