จำ

Borrowed from Old Khmer ចាំ (cāṃ), ចាំម (cāṃm), ចាម៑ (cām), ចំ (caṃ), ចម៑ (cam, “to remain, to stay; to bear in mind, to memorise, to recall, to remember; etc”). Cognate with Modern Khmer ចាំ (cam); Lao ຈຳ (cham); Northern Thai ᨧᩴᩣ. Extended as Thai จำนำ (jam-nam), ประจำ (bprà-jam).

The "keep in mind" and "required" senses are considered etymologically equivalent by TDP.

จำ • (jam) (abstract noun การจำ or ความจำ)

1. (archaic) to stay or remain; to cause to stay or remain.
2. to keep; to hold; to confine; to detain; to imprison.
3. to keep in mind; to bear in mind; to memorise; to remember; to recall.
4. (somewhat elegant or archaic when used alone) to need, be needed, be required, or be forced (to do something).

• “จำ” in Thai Dictionary Project (TDP) (UC Berkeley 1964) (plus additional data from the Royal Institute of Thailand (RI) and NECTEC's LEXITRON project (LEX)). Searchable online at SEAlang.net.