There are six pairs of demon guardian statutes at the entrance gates to temple in the gallery. The are the main Giants of the Ramayana. They stand facing the ordination hall (Phra Ubosoth) meaning that they are guarding the Emerald Buddha inside from all evil spirits.

These demon guardians were built in the reign of king Rama III, each one describing an important character in the Ramakien story. The green one describes Tosakanth, the demon King and red one represents Sahassadeja, one of Tosakanth’s warrious.

source : Tourist Guide to Thailand book,Thailand-sawasdee.blogspot.com