Visit the fish.
About 15km. South of PKK is the King Mongkut Memorial Park of Science and Technology which was set up in memory of the eponymous monarch visiting with his son, Prince Chulalongkorn to see a solar eclipse in 1868. Unfortunately, he got more than he bargained for, contracted malaria and died. There is not much in the park itself but the Waghor Aquarium in the park is very good with a huge selection of fish and marine life. It also has a huge selection of the noisiest schoolchildren I have ever heard, but that's life, I suppose.
Admission to the park is free but there is an admission charge for the Aquarium itself. It is open from 0830 until 1630 daily. For disabled visitors, I would make enquiries before visiting as I did not see any provision for wheelchairs to go down to the lower level where the aquarium is although access from the rear may well be possible. Allow yourself no more than an hour for a really good look round.