Mrs. Piggle-Wiggle
Flat Stanley
McBroom books by Sid-Fleischman
Gail Carson Levine’s Princess Tales
My Father’s Dragon
Boxcar Children
Beverly Cleary
Magic Treehouse
Pippi Longstocking
Just-So Stories by Kipling (get an illustrated version)
Not a chapter book, but I highly recommend The Quiltmaker’s Gift by Jeff Brumbeau. It has more text than an average picture book, gorgeous illustrations, and a charming story.
Here’s a related thread you might find helpful:
Chapter books for kindergartener
https://www.dcurbanmom.com/jforum/posts/list/940610.page