Thank you ธ.วั ช ชั ย :  Your info is much appreciated.

I picked this word เท็จ for its many curios.

1) Where/What language this word เท็จ comes from? เท็จ does not look like a basic/native Thai word. (The word เผด็จ seems to have come from Khmer language).

2) I looked up Pali and Sanskrit dictionaries and I could not find any possible 'root'. (Thais are more familiar with มุสา as in  ...มุสาวาทา เวระมะณี...)

3) a possible etymology may be the Latin word "data" (เด ต้า --> เดต ตะ --> เทจ จะ --> เท็จ) but this is at odds with etymology of เผด็จ). Thai interpretation of เท็จ is quite compatible with "data". We can have "real data" (เท็จจริง) or "false data" (เท็จเทียม). If this is the case then there should be a Pali or Sanskrit 'equivalent' of Latin 'data' as these languages have many words in common. (???)

So, what do you think? May be some Thai language teachers can help me here. Please!