I don’t think either Putin or Lukashenko will order Belorussia to invade Ukraine any longer. The Belarusian military might be almost as likely to advance toward Minsk if forced to fight today. Seeing Russia’s loses they have less of a reason to fear Russia and more of a reason to fear Ukraine.
At this point Putin seems to do nothing right and attaching your fortunes to him seems like a bad bet.
Belarus is kind of large country, but pretty sparsely populated. They do not have too much an army.
Mostly NKWD troops.