The ancient city is the park close to Bangkok where they build small copies of building from all over Thailand.

It is a good idea to visit Luang Prabang from the north of Thailand. The distance between Chiang Mai and Luang Prabang is only 750km. But due to a border crossing and bad road conditions, It can take up to 24 hours. 

Siam park city is located in suburbs of Bangkok. The best way to get there is by Taxi. Just tell the driver "Siam park city". Usually, it costs about 300 baht.

First time I visited it in 1996. I was only 6 years old. We visited it about once a month. It is one of most excited experience, I remember from living in Thailand.

Check the site of the place: https://www.siamparkcity.com/en/main.php