Thailand is located at the center of the Indochina peninsula in Southeast Asia. It is bordered to the north by Myanmar and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia and to the west by the Andaman Sea and the southern of Myanmar. Thailand has total area of 513,115 square kilometers from 5° 27' to 20° 28' north and 97° 21' to 105° 38' east (Royal Instituted, 2002).  Most of Thailand climate is tropical wet and dry or savanna climate. According to the southwest monsoon from the South China Sea, the tropical cyclone and the northeast monsoon from China are influence climate of Thailand that divided into three seasons, summer, rainy season and winter. The average temperatures are 18-34 ° C and annual average rainfalls are 1,500 mm (Tourism Authority of Thailand, 2000c) 
Thailand is located between two biogeographical region, Indochina biogeographical region and Sunda-typical of Malaysia, Sumatra, Borneo and Java biogeographical region that makes Thailand is the center of three floristic elements such as Indo-Burmese elements, Indo-Chinese element and Malesian elements. The Plant community is Thai monsoon forests, Indochina forest and Malayan forest, overall called the Tropical Dry or Deciduous Forest (Santisuk, 1989) . According to Smitinand (1989)  Thailand can be divided into seven floristic regions i.e. the Northern (N), North-eastern (NE), Eastern (E), Central (C), South-eastern (SE), South-western (SW), and Peninsular (PEN). van Welzen et al. (2011)  divided area into four floristic regions, Peninsular Province (extending in the South-eastern), Northern Province (with extensions into the South-western and South-eastern), Eastern Province and the Central Lowlands.
Phu Hin Rong Kla National Park is the 48th national park in Thailand, covers an area of approximately 307 square kilometers and parts of Phitsanulok, Loei and Phetchabun province. It was a stronghold of communist party that detrimental to the nation stability in 1968-1972. After the situation ended, the government has controlled the area and established the national park. In general, Phu Hin Rong Kla National Park is the mountainous area with many peaks, the highest peak is Phu Mahn Khao peak located in Phu Thab Boek area. Phu Thab Boek area in Phu Hin Rong Kla National Park covers an approximated area of 30 square kilometers and ranged in elevation from 1,600-1,800 meters above mean sea level. For the plant exploration and collection in the area are most flowering plants and a few pteridophytes in specific area. But the collections of pteridophytes in Thailand show that 118 species are from Phitsanulok, 218 species from Loei and 46 species from Phetchabun. It seems that these provinces are riches in pteridophytes diversity (Tagawa and Iwatsuki, 1979, 1985, 1988, 1989).     Moreover, Phu Thab Boek area is located in North Eastern floristic region and there are few data about diversity of pteridophytes in area that higher than 1,500 m above mean sea level.
It is necessary to explore pteridophytes diversity in Phu Thab Boek area, Phu Hin Rong Kla National Park because the risk of deforestation from road construction may lead to the risk of pteridophyte extinction. Moreover the biodiversity knowledge will be increased and the data from this study can be useful in biodiversity conservation in protected area in the future.
- , The Royal Institute Thai Gazetteer, 4th ed. Bangkok: , 2002.
- , Thung Saleng Laung, Phu Hin Rong Kla, coniferous Forest, grassland and rock platform of Phetchabun mountains. Bangkok: Amarin Printing and Publishing, 2000.
- , “Flora of Thailand: past present and future”, 7th Biolocial seminar: Biodiverity in Thailand. Chiang Mai, 1989.
- , “Thailand”, in Floristic Inventory of Tropical Countries: Status of Plant Systematics, Collections and Vegetation, Plus Recommendations for the Future, New York: New York Botanical Garden, 1989, pp. 63-82.
- , “The current and future status of floristic provinces in Thailand”, in Land use, climate change and biodiversity modeling: Perspectives and applications, Hershey: IGI Global, 2011, pp. 219-247.
- , “Pteridophytes”, in Flora of Thailand, vol. 3, Bangkok: The Tist Press, 1979.
- , “Pteridophytes”, in Flora of Thailand, vol. 3, Bangkok: Phonphan Printing Company, 1985.
- , “Pteridophytes”, in Flora of Thailand, vol. 3, Bangkok: Chutima Press, 1988.
- , “Pteridophytes”, in Flora of Thailand, vol. 3, Bangkok: Phonphan Printing Company, 1989.