笑いごとではすまなくなる。

laughing matter

indicates location of action; at; in; indicates time of action; indicates means of action; cause of effect; by; and then; so; indicates continuing action; indicates certainty, emphasis, etc.

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

to finish; to end; to be completed; to merely result in something less severe than expected; to feel at ease; to feel unease or guilt for troubling someone; to be sorry

to become; to get; to grow; to be; to reach; to attain; to result in; to prove to be; to consist of; to be composed of; to succeed; to be complete; to change into; to be exchanged for; to play a role; to be promoted; to do ...