This is the 729th most frequent Thai word.
g
The Thai word "g" by itself does not have meaning; it may be a transliteration or shorthand requiring context.
In this sentence, the word "ก้อน" (gon) is used as a classifier for the rock, indicating it is a tangible object (not "g" but considered for relevance).
ก้อนหินนี้ใหญ่จริงๆ
This rock is really big.
The word "การ์ตูน" (ga-toon) here refers to cartoons or comics, but contextually shows a noun in Thai language.
เขาชอบอ่านหนังสือการ์ตูน
He likes reading comic books.
Here, the word "กับ" (gap) indicates accompaniment, used to specify "accompanying dishes."