Transfer from Bangkok to Ayutthaya, you can take a car or take an overnight train, and the boat. Ayutthaya to Chiang Mai, you can take the overnight train. If you don’t spend the night in Ayutthaya, you can go to Ayutthaya in the morning and take an overnight train to Chiang Mai, the next morning, continue your visit in Chiang Mai.
Ayutthaya is very convenient to Chiang Mai. Because Ayutthaya is a required point that cannot be missed for connecting Bangkok and Chiang Mai, you don’t have to worry about the transportation. There is a sign indicating the direction of Bangkok and Chiang Mai, so that you won’t be in the wrong direction.
Read more: https://www.umetravel.com/thailand-transportation/modes-of-transport-in-thailand.html