Keep in mind that Muay Thai also has the Charn Gerk. Theirs is usually more devastating as they train their roundhouse kicks with more power. The good thing is they rarely execute this in the ring as this is considered a street technique best used when wearing shoes.
An upwards charp chui is useful when they are attempting to clinch. Opening up an attack with a powerful gwa choy opens up their defense. The way we train our front thrust kick from the lead leg has surprised a number of Muay Thai guys I have trained with, and I believe the speed and power we can generate from this kick is something we can capitalize on.
Been chui's are also something they don't expect quite often. Just feint with a biu jee strike and execute the backfist when they guard their face and eyes.
The best defense is a strong offense; therefore, train harder than your enemy. Real muay thai fighters train very hard, so your best bet is a lot of conditioning and a lot of swift, powerful techniques that are easy for you to execute. Anything fancy and a push-uppercut-hook-roundhouse or knee combo will send you on your ass.