Chiang Rai

Thailand’s northernmost city is small and quiet, providing the ideal launching point for treks through some of nature’s more spectacular settings.
Thailand’s northernmost city (about 180 km from Chiang Mai), Chiang Rai dates back to 1262. The atmosphere here is more relaxed than in Chiang Mai, but it is a good starting point for treks into rural areas.
Northern TemplesTemple enthusiasts should visit Wat Phra Kaew, which once housed the Emerald Buddha, Thailand’s most sacred Buddha image, during periods of turbulence between Thailand and Laos in the 16th – 18th centuries. Formerly kept at several northern temples, the image is now safely ensconced in the temple of the same name in Bangkok. Chiang Rai also has a Wat Jet Yot. This one has an interesting Thai astrological fresco on the wooden ceiling of its main building. Other temples to see are the Shan/Burmese Wat Paa Kaw and Wat Phra That Doi Thong, which overlooks the scenic Kok River.
Hill TribesYou can take treks to hill tribe villages from numerous agents in Chiang Rai. Ethnic groups in the province include the Karen, Lisu, Lahu, Akha, Meo and Yao. Booking treks through guesthouses is probably better and cheaper, as they have been operating longer than agencies and may employ more experienced TAT (Tourism Authority of Thailand) guides. You can also take boat rides to small but interesting towns and hamlets along the Kok River.
Tribal HandicraftsThe Hill Tribe Education Center on Thanalai Road has informative slide shows and displays of tribal artifacts and handicrafts in its museum section, open from 9 a.m. to 8 p.m. every day. Handicrafts are for sale on the 1st floor.
Reference : http://www.circleofasia.com/Chiang-Rai-Thailand.htm
Korat
Though in modern times it is a developed industrial town, there is much to see of historical interest nearby.
Twin TownsDuring Ayutthaya’s prominence, two towns united to form Nakorn Ratchasima, commonly known as Korat. Now a busy industrial city, it shares many of Bangkok’s features, both good (nightlife and bazaars) and bad (pollution). If you are coming from Bangkok and desire peace and quiet, nearby Phimai is a good base from which to visit Korat during the day.
US Vets CafeteriaThere was an American air base near Korat during the Vietnam War, and you can still visit the Veterans of Foreign wars Cafeteria on Phoklang Road. Some ex-GIs have since settled here.
Historical MonumentsAppealing temples include Wat Sala Loi, with its junk-shaped chapel, and Wat Phra Narai Maharat, which houses Korat’s city pillar and a Khmer statue of Vishnu. Mahawirawong National Museum houses more Khmer stonework and other artifacts. Also interesting is the Thao Suranani Memorial, which honors a Thai woman who, with her citizens’ army, expelled Lao aggressors in the early 1800s. Locals make offerings to her spirit for protection, and traditional Korat folk singing (financed by grateful worshippers) is a nightly event opposite the memorial. Thao Suranani also has her own festival; Korat’s biggest, from late March to early April. This involves folk singing, drama (Li-Kay), parades and beauty pageants.
Khmer Ruins60 km outside Korat, Prasat Hin Phmai National Historical Park near Phimai contains impressive 10th and 11th century Khmer ruins older than Cambodia’s Angkor Wat. The new Phimai National Museum displays Khmer sculpture from elsewhere in Thailand.
RainforestIn the same province, Khao Yai National Park is reputedly one of the world’s best: you can hike through superb rainforest teeming with wildlife.
http://www.circleofasia.com/Korat-Thailand.htm