Dear Yong Peng,

OYP> can I say, for the verse below, aha.m is dropped off to comply
OYP> metrical rules in Pali, or is it common even in prose? What about in
OYP> other languages with verb conjugations similar or close to Pali?

In Ukrainian such use is quite allowable, though mostly in those
contexts when the agent of the action is too obvious or has been
indicated in previous sentences, and also in conversations and verses.

In Pali such usage occurs even more often.

metta,
Dimitry