I had some friends come to visit recently. I recommended ...
An all day pass on the skytrain green line, getting off at various points of interest (including JJ Market).
An all day pass for the tourist river ferry, again off/on at points of interest
A half day at the Royal Palace/Wat Phra Kaew.
A dinner cruise on the river on their last night.
They had a great time and can't wait to come back.
My granddaughters are due to visit next year. They are dog lovers, so I will take them to the Husky Cafe (True Love at Neverland) in Phaya Thai. My wife, daughter and I had a great afternoon there last year (to my surprise, as I am not really a great dog lover).