On what condition did Maharaja of Manipur sign the 'instrument of accession' with India?

The internal autonomy of the state will be maintained.

Manipur was a princely state with its own monarch, Maharaja Bodhchandra Singh, and a distinct political and administrative system.
It enjoyed a measure of autonomy under British colonial rule.
Maharaja Bodhachandra Singh of Manipur signed the Instrument of Accession with the Indian government shortly before Independence.
The agreement ensured that Manipur would maintain its internal autonomy.