Can a bad karma happen just only with a thought without any physical or verbal action? Do we collect bad karma just only with an instant thought without any physical action or verbal action?
Yes, from multiple suttas we see that karma can be done by way of the mind and intentional thoughts only. In fact, according to the first verses of the Dhammapada, the mind precedes all mental states. It's more important than words and actions.
From Nibbedhika Sutta:

&quot;Intention, I tell you, is kamma. Intending, one does kamma by way of
body, speech, &amp; intellect.

From Mahakammavibhanga Sutta:

After doing an intentional deed to be experienced as pleasant by way
of body, speech, or mind, one feels pleasure. After doing an
intentional deed to be experienced as painful by way of body, speech,
or mind, one feels pain. After doing an intentional deed to be
experienced as neutral by way of body, speech, or mind, one feels
neutral.”

From Bhumija Sutta:

&quot;When there is a body, pleasure &amp; pain arise internally with bodily
intention as the cause; or when there is speech, pleasure &amp; pain arise
internally with verbal intention as the cause; or when there is
intellect, pleasure &amp; pain arise internally with intellectual
intention as the cause.

From Kamma Sutta:

And what is new kamma? Whatever kamma one does now with the body, with
speech, or with the intellect. This is called new kamma.&quot;