[TabiFolk]

According to Cory Lee it is fairly wide open, but not much more in terms of a description.

https://www.curbfreewithcorylee.com/2014/12/04/wheelchair-access-bangkok-thailand/

According to wheelchairtraveler.org,

The palace grounds are partially open to the public and are a must-see attraction for visitors to Bangkok. The lawns and gardens are wheelchair accessible.

But he also goes on to say that the Temple of the Emerald Buddha only has steps.

https://wheelchairtravel.org/bangkok/attractions-sights/

Hope this is helpful to get you started.

[mrtiesto]

Its been a few years but I’m pretty sure that it is not easy to get there on public transit, so you may want to hire a wheelchair taxi.  Wheelchair Holidays Thailand has a pretty big one that can take power wheelchairs: https://www.wheelchairtours.com/wheelchair-taxi-rent

From what I remember, even if some areas were not accessible, the grounds are very big and worth seeing. Some of the steps under  archways had slopes.

You might be able to check it out on Google Maps Street View…

[Unknown Member]

From what I know getting there is not very easy. Also tends to be very crowded even if it is wide.