Doi Inthanon located in Chiang Mai Province, Doi Inthanon National Park encompasses the highest mountain In Thailand, Doi Inthanon, as well as several lesser summits. The park was refered to as Doi Ang Kha. Prince Intharawichayanon, the last ruler of Chiang Mai, realized the importance of the country's forests especially those in the north where they serve as the sources of headwaters for much of the country. He helped support people to study the areas. He requested that his remains be placed on the summit of Doi Ang Kha. After his death, the mountain was renamed Inthanon, a shorten version of his name. Today, visitors to the summit can see the remains of the prince there.

The Park is ruggedly mountainous. Doi Intanon, the highest peak stands at 2,565 meters above sea level. Lesser peaks include Doi Hua Luang (2,330 meters). The park is the source of headwaters for the Mae Klang, Mae Pako, Mae Pawn, Mae Ya, Mae Cham and Mae Khan rivers. The water from the park helps generate electricity at the Bhumipol dam site in Tak province.

The doi (mountain) is largely a granite batholith intruding a southerly extension of the Shan Hills range and forming the divide between the Nam Mae Ping river to the east and the Nam Mae Chaem river to the west. Lower elevations in the most easterly pant of the park are limestone formations and contain a number of caves.

Formerly known as Doi Angka, the mountain now bears (since 1899) a shortened version of the name of Chiang Mai's last sovereign, King Inthawichayanon. During his reign, he had, with great foresight, expressed his concern for the forests of the northern hill country as the watershed for all of central Thailand. The modern study of rain forest hydrology has borne out his early convictions and given substance to Thai folklore which describes this hill region as the home of the Phiphannam, the 'spirit who shares water'. Before the King died near the turn of this century, he commanded that his remains be placed at the top of this mountain: his ashes at the summit stupa are visited by thousands of people each year.

The park covers an area of 48,240 ha. Its lowlands below 800 meters in elevation are warm and very dry during the rain-free season, but the summit of Doi Inthanon, at 2565 meters, has a climate more like Canada than Thailand. The temperature has been known to drop as low as -8 degrees C. and frosts are not unusual during the cool, dry season. January is the coldest month: an average nighttime temperature is 5.5 degrees C. At any season, Doi Inthanon is a comfortable reprieve from the heat of the lowlands. At altitudes above 1000 meters, rainfall exceeds 2500 mm, considerably more than at nearby Chiang Mai. Even in the dry season, November to April, there is rare but occasional rain or the summit may be shrouded in cloud for a part of the day; persistent mist is an important factor in the maintenance of moist forest there.

Rhododendron The various sub montane forest formations at higher elevations are a unique asset of the park. They have dominant species belonging to temperate climate families rather than tropical. The summit area supports the only red rhododendron in Thailand (R. delavayi); it blooms from December through February. There are also two white-blossomed species abundant on Doi Inthanon which are restricted to only a few other sites.

Where mists are persistent, the slopes carry a moist hill evergreen or 'cloud forest' with many epiphytes, plants which live on tree trunks and branches but do not receive their moisture and nutrients from the host tree as do true parasitic plants. Instead, they are nurtured by the accumulation of dust particles and humus around their 'root' area and the moisture retained there, augmented by frequent bathing in cloud and mist. Epiphytic orchids are also abundant, along with lichens, lianas and fern.

Road At mid-elevations, 800 - 1500 meters, two species of pine are present, Pinus merkusii mixed with dipterocarp in the lower range, and P. kesiya with oak and laurel on drier slopes in the upper range. The pines are thought to be a relic from a prehistoric cooler climatic period when flora from the Sino-Himalayan region migrated southward. At the mid-elevations of the park, much of the forest has been removed by the activities of swidden cultivators and the slopes have converted to fire climax grasslands.