Thailand Reisetipps

hello everyone,
I am planning a 16 day trip in Thailand. I will start in Bangkok and head towards south to Khao Sok National Park. My final destination will be koh samui to relax and enjoy my last couple of days.
My question:
I want to have a few stops between Bangkok and Khao Sok National Park. What would u recommend me? I want to experience some local stuff, nature, hiking, beaches, motorcycling.
I take into consideration to stop at Phetchaburi and Hua Hin. What u guys can recommend me?
Thanks a lot in advance.

Kind regards
Jörg

Two recommendations:
1) Samut Songhram (for a few days): train market, floating markets (e.g. Amphawa, Damnoen Saduak), caves (Ratchaburi and Petchaburi area) - best to have a private car to be flexible
2) Khao Sam Roi Yot NP (40 km south of Hua Hin)