A good way to study about Himmapan creature is to visit many sites available throughout Asia. Look closely within Buddhist temples, and Hindu temples, Ancient Palaces and you will find a wealth of Himmapan creatures making appearances here and there.
 
For starters, Bangkok is a good place to start learning about Himmapan creatures as there are many temples and museums which contain Thai culture and artifacts. Listed below are some places I recommend visiting.

Wat Phra Kaeo and the Grand Palace This is Bangkok’s premiere tourist attraction. This complex was constructed in 1782 as King’s palace and the resting place for Phra Kaeo (emerald Buddha)—Bot of the Emerald Buddha. One of the most spectacular sights in the complex is the 179 rooms with mural paintings depicting the epic tale of Ramakien or Ramayana. (Here you will find a lot of Himmapan creatures) Open: Daily from 8.30am-3.30pm. Admission: Thai-Free                    Foreigner-200 Bht Tel: 0-2222-8181 Web: www.palaces.thai.net

The National Museum Within the walking distance of the Grand Palace is one of the largest and most comprehensive museums in Southeast Asia. Bangkok's National Museum houses a vast collection of artefacts found in all parts of the country ranging from neolithic times, Sukhothai, Ayutthaya to the Bangkok period. You will see quite a few Himmapan creatures on door and window panels.   Open: Wed-Sun from 9am-4pm. Admission: 40 baht Tel: 0-2224-1333 Web: www.thailandmuseum.com

Wat Arun (The Temple of Dawn) The mixed culture temple between Chinese and Thai locates along the Chao Phraya river bank. Here you will find many strange stucco Lions and Ghilens. Open: Daily 7.30am-5.30pm. Admission: 10 baht Tel: 0-2891 1149

Wat Po Considered the first University of Thailand, this temple houses beautiful wall mural depicting life of Lord Buddha. Some drawings of Himmapan creatures can be spotted here as well. Open: Daily from 8.30am-9pm. Admission: Thai-Free                    Foreigner-20 Bht Tel: 0-2222 5910, 02226 2942

Wat Sutat Wat Suthat and The Giant Swing Located on Bamrung Muang Road, this temple is noted for its superb 19th century murals in the main chapel.   Open: Daily from 8.30am-9pm. Admission: 20 baht Tel: 0-2224-9845, 0-2222-9632 Web: www.watsuthat.org

Wat Benchamabopit This unique marble temple was constructed during the reign of King Rama V. It employs European ecclesiastic details, such as stained glass windows, and contains a superb cloister collection of bronze Buddha images.   Open: Daily from 8.30am-5.30pm. Admission: 20 baht Tel: 0-2281-2501, 0-2628-7947

Ancient City The Ancient City, like a door opened to the cultural in heritage of Siam. The visitors are able to see the continuity of the history, arts, cultures, religious, thoughts as well as the believes of Thai talents. It shall reflect to Thai fundamentals and the varieties of the cultures on Thai territories.     Open: Daily Admission: Adult-150 baht                    Child-50 baht Tel: 0-2371-3135 Web: www.ancientcity.com

Erawan Museum This is a very well maintained museum with many interesting ancient art items and artifacts. Around the area is the immitated Himmapan garden with stucco Himmapan creatures.     Open: Daily Admission: Adult-150 baht                    Child-50 baht Tel: 0-2371-3135 Web: www.ancientcity.com