We ended up in Ayutthaya as it was the only town in which we could catch the train to Chianmg Mai without going back to Bangkok.
Turns out this sleepy city was the capital of Thailand more than 400 yrs ago! The town is one big ruin now with a few not-so-modern buildings and restaurants scattered among the different former sites of palaces, temples, etc -- we descended narrow, steep steps of one of them andsaw some of the original walls and murals. That was awesome.
Seeing the sights here took all of an hour. As we still had 5 hours to kill before the overnight train to Chiang Mai, we did what the made most sense -- stopped in the nearest pub and tossed back a few cold beers(so we could sleep on the train, of course!!!)