Khao Yai National Park and Elephant Ride

The round trip takes around ten hours and you can find various tour operators charging around $80. You will get to see the oxcarts in the paddy fields, tigers, black bears and leopards. Also, an elephant ride through the jungle is something to look forward to. This park is around 175km from Bangkok city. 

You can stop by to buy tropical fruit from the roadside stalls. 

Jim Thompson House

website: http://www.jimthompsonhouse.com/

American Jim Thomspon turned the silk manufacturing into the industry in 1959. He bought this piece of land and build wooden homes that were constructed in a jungle-like garden.  You can enjoy a friendly tour from 9am-5pm in English

Choa Praya River Dinner Cruise

This is a beautiful way to enjoy the waterside Bankok on a 2.5-hour dinner cruise with live entertainment and music. The evenings are normally pleasant and both sides of the river are lit with beautiful lights. You will see historical temples, modern hotels, shopping malls. Make sure you make your booking in advance from one of several tours. You can also rent a boat for around 1500Bhat and enjoy one hour of a river cruise. During the day time there is lots of humidity, therefore, make sure the weather is fine and not too humid. 

website: http://www.thaicruise.com/