It is speculated that Ram Khamhaeng expanded his kingdom as far as Lampang, Phrae, and Nan in the north, Phitsanulok and Vientiane in the east, the Nakhon Si Thammarat Kingdom in the south, the Mon kingdoms of what is now Myanmar in the west, and the Bay of Bengal in the northwest. However, in the "mandala" political model, kingdoms such as Sukhothai lacked distinct borders, instead being centered on the strength of the capital itself. Claims of Ram Khamhaeng's large kingdom were intended to assert Siamese dominance over mainland Southeast Asia.