What is the best connective word to make these two thoughts into one sentence 1 I like play baseball 2 throw a ball very well?

The best connective word to make the two sentences into one would depend on the intended meaning. Here are a few options:

To emphasize your ability to throw:

* because: "I like to play baseball because I throw a ball very well."

* since: "I like to play baseball since I throw a ball very well."

To indicate that your throwing skill is part of enjoying baseball:

* and: "I like to play baseball and throw a ball very well."

* as I: "I like to play baseball, as I throw a ball very well."

To show a contrast:

* but: "I like to play baseball, but I throw a ball very well." (This emphasizes your skill while implying you're not necessarily the best player overall)

The best option depends on the nuance you want to convey.