Beating General Kwai is a slightly hard thing to do since he sends his heavy armor not in the initial attacks but only a while into the game.
Beating Kwai with GLA is probably one of the harder tasks, since you do not have proper base defence and no heavily armored units.
Ignore building your base defence. It is useless throughout the entire game. Do, however, build a small group of RPG troops, scorpions, and 4-5 Quad cannons to serve as your anti air. Build your palace at the front of you base to serve as the main cannon fodder (only when it’s loaded up with infantry) and make sure that there is always a worker behind it to fix it fast.
Try to save up a tiny bit of money for black markets, but do not make it your primary goal. Hold out with your scorpions and RPG troops until you get 3rd ranked and by the 20% bounty, which will increase your income tremendously. After you help out for that long and can replace any fallen tanks with ease, begin construction of your black markets.
Once you have a sufficient cash flow, construct 3 other arms dealers to have a total of 4. Have scorpions pour out of 3 and quads steadily stream out of the other. You may want to build angry mobs since they are a powerful addition when dealing against buildings. Once a group has accumulated, reset the rally points to his base and charge with everything you have. Try to drop in the anthrax bomb and ambush to stop the majority of tanks from attacking your force, at least for a while.
Beating Kwai with USA is pretty easy. Simply concentrate your cannons in a small ring around your base, so that they overlap their range, allowing for easy relay of targets. When you have 15-20 turrets in a tight ring, proceed with the construction of supply drop zones and then 4-5 factories to send out a constant stream of avengers and tanks.
If you are Super weapon general, defending is a whole lot easier, but attacking mught prove to be a pain. Try using one factory to build avengers and 6-7 factories to make missile defenders. Their sheer weight of numbers plus the fact that he doesn’t have artillery would prove you victorious. Use your avengers to deflect most of the missile fired by the bunkers and Migs.
The defence best suited for this stage is bunkers. Build up your defensive ring in a tight formation around your base, using as little gatling cannons as possible since the tanks have a tendency to attack them the most. Once you held out for long enough and built enough hackers, make a stream of nuke cannons and overlords/attack outposts. Again, once a group has formed send on onward while constantly refilling you factories.