Once you are done with Pattaya and Bangkok you want to explore more. Here is the itinerary north of Bangkok.
A day excursion from Bangkok. You can access it by train or by road. If you are interested in the history then this second world war site is of importance to you. During the end of the second world war Japanese had conquered this area and they were planning a rail line to Burma and India from here. The labour was done by captured British prisoners of War. The bridge on the river Kwai movie has showcased it well. Kwai river bridge is the most popular site here.
Ayutthaya was the capital of Thailand before it is moved to Bangkok. The name is pronounced as Ayodhya which was capital of Shri Ram in India. King of Thailand use title of Ram before their name. Present King of Thailand is Maha Vajiralongkorn, Ram X.
From Bangkok it is 81 km north well connected by road and rail. It lies on the banks of the Chao Phraya River. Important sightseeing places at Ayutthaya are Ayutthaya Historical Park which is a world heritage site. Wat Mahathat, Wat Yai Chai Mongkhon, Wat Chai Wattanaram, Reclining Buddha Sai Yat are important sites. You can easily spend 2 days here if you are interested in archeology or Buddhism. Cycles are available are rent and are highly recommended wandering very large campus of historical park.
Museums in the near vicinity of historical park are worth a visit.
Sukhothai was another capital of Thailand. From Ayutthaya it can be approached by Road or by train to Phitsanulok which takes about 5 hours. Distance between these two places is about 363 kilometer.
This is yet another world heritage site. The Sukhothai historical park has two main zones, Central zone and North zone. The Central zone takes time to visit important monuments there. Opposite to central zone is Sukhothai National Museum. Post lunch you can visit the North zone which has Big Buddha in Wat Si Chum. Another famous Wat in north zone is Wat Phra phai luang.
This is the entry point to North of Thailand. It has an international airport. Can be reached from Bangkok by road / rail or domestic flight. Being close to hills weather in Chiang Mai is pleasant and cooler than Bangkok.
Old Chiang mai city has fortified walls with moat filled with water and bastons on four corners. There are many famous Wats inside the fortified city. The place is full of eateries and tourists.
Many adventure activities are centered at Chiang Mai. Be it Elephant orphanage center, Trekking, Rafting, Zipline, Shooting, Cycling. The samoeng loop which is around 100 km circular road in hilly terrain can be explored using rented scooters.
Chiang Rai is 3.5 hours drive from Chiang mai and one can spend 2 days here totally cut off from the hustle and bustle of touristic thailand.