Tai-Ahom kingdom of the Brahmaputra Valley (Assam), founded by Sukaphaa, a Tai prince from Mong Mao; grew from a small wet-rice polity into the dominant power of the upper Brahmaputra, repeatedly repelling Mughal invasions across the 17th century, most famously at the 1671 Battle of Saraighat.
Weakened by internal succession crises and Burmese invasions in the early 1800s, the kingdom passed to British East India Company control via the Treaty of Yandabo in 1826, ending the First Anglo-Burmese War.
The atlas holds 3 border frames for Ahom Kingdom — the shape you scrub through changes in 1228 · 1446 · 1565.
Polity-specific: Gait's classic scholarly history of Assam is built substantially around the Ahom dynastic chronicles (buranjis) and remains the standard English-language reference; verified on Open Library.