If you visit the Royal Palace cover up arms and legs, long sleeves & trousers
You can walk from there along river to Wat Po the temple of the reclining Buddha
Then get ferrry across river to Wat Aran temple of the dawn
If you like shopping Chatuchak market or BTK indoor market
China town good for street food and browsing
There is a train metro and sky train or tuk tuks and boats on the river to travel
You can buy a map and travel round yourself. If you look lost people will usually point you in the right direction or hire a local guide or visit via an organised tour
The floating markets are in towns a couple of hours away from Bangkok
The city is busy, but there a places of calm too