I found some children stories from Pan for Kids that are available on the internet for free.

Plan for Kids

If you can’t read Thai, click on the titles of the stories which are located above and below the radio dial icon.

If you’re intermediate – advance reader, a website called Fringer offers a wide variety of text in Thai that you can easily use to practice your reading. I particularly like The Missing Piece Meets the Big O story.

Have fun. =)