Explanation:

During the British rule, the Khasi domain was divided into the Khasi states and British territories. At that time, the British government had no territorial right on the Khasi states and they had to approach the chiefs of these states if they needed land for any purpose.
After independence, the British territories became part of the Indian dominion but the Khasi states had to sign documents beginning with the Standstill Agreement that provided a few rights to the states.
The 25 Khasi states had signed the Instrument of Accession and Annexed Agreement with the Dominion of India between December 15, 1947, and March 19, 1948. The conditional treaty with these states was signed by Governor General Chakravarty Rajagopalachari on August 17, 1948.
The Khasi states, though, did not sign the Instrument of Merger unlike most other states in India.