Play video content EXCLUSIVE TMZ.com

Kesha's making a name for herself in a new field -- the wedding officiant biz -- and she just booked another couple of happy clients.

The singer was at the premiere of her new documentary, "Rainbow: The Film," at Metrograph theater in NYC Thursday night when a couple approached her and asked if she'd marry them ... and she said she'd love to!

This isn't just all talk from Kesha either -- not only did she hook the ladies up with her scheduling peeps ... but she's got a happy history of officiating same-sex weddings. She's already done 3.