Can an old bad laptop be at fault for the high ping?

I've been pinging servers for 3 weeks now. Had earlier so 25-28. Now it's 35-50 and it's rocking extremely. My line is ok, my router up to date and play over Lan. Can the laptop be to blame?

No. Normally not. However, you must make sure that all network drivers (ie the router and PC / laptop) are up to date. Ping is the Internet's reaction time, so normally it has nothing to do with a bad laptop.

No! You could theoretically play on a toaster, which does not change the connection.

It also depends on the condition of the game.
Especially with MMOs that were released freshly or in the EarlyAcess, you can get some ping-spikes, because the servers are either overloaded or need to be optimized properly. Or does it depend on where the servers are?

In a game where you only have one NA server at your disposal, even a 150k line will not help you to get a better ping.