This underglaze-black, hollow stoneware stair-head or possibly a roof tile is in the form of a fierce and expressive makara with a naga being emitted from its mouth.
Ordination halls (ubosot) and assembly halls (wihan) generally were constructed of wood during the Sukhothai period but with such glazed terracotta or stoneware elements. As these buildings deteriorated or were replaced, the terracotta ornaments survived and thus became available.
Most probably the example here was made at the kilns in Sukhothai or Si Satchanalai. (The two sites competed with one another but the Sukhothai kilns commenced operations slightly after those at Si Satchanalai.)
It is tall, sculptural and free-standing. The makara has a row of pointy teeth, a flowing, pierced mane and a high pierced crest. The body is scaly and there is a petalled collar. Two short legs are denoted on either side.
Several horns are broken away which is typical of these unless they have been restored. The crest atop the head is present and complete although seems to have been reattached. The condition is stable, and there are no other significant losses.
See Brown (2009, p. 59) for a similar example. Related examples also are illustrated in Rooney (2013), Sumner & Osborne (2001, p. 71) and in Richards (1995, p. 69).
Overall, the example here is of unusual size and is particularly sculptural.
References
Brown, R., The Ceramics of South-East Asia: Their Dating and Identification, second edition, Art Media Resources 1988.
Brown, R., Southeast Asian Ceramics Museum, Bangkok University, Bangkok University Press, 2009.
Guy, J., Thai Ceramics: The James and Elaine Connell Collection, Asian Art Museum of San Francisco/Oxford University Press, 1993.
Richards, D., South-East Asian Ceramics: Thai, Vietnamese, and Khmer – From the Collection of the Art Gallery of South Australia, Oxford University Press, 1995.
Rooney, D., Ceramics of Seduction: Glazed Wares from Southeast Asia, River Books, 2013.
Sumner, C. & M. Osborne, Arts of Southeast Asia: From the Powerhouse Museum Collection, Powerhouse Publishing, 2001.