I would not recommend same sex bunnies as if they are not brought up together there is a higher chance of fighting between them. Most people I have incountered say the best bet is introducing a netuered rabbit of the opposite sex.
I had 2 females (both neutered) who were raised together and were fine, then one died so I did some research and adopted a male neutered rabbit from a rescue centre there were a couple of scraps whilst they were finding out the boundaries, but now they are completely in love with each other and spent lots of time together. they are both in an outside hutch with a big homemade run so they can come in and out as they please.
Thumping would suggest that there is something that is making the rabbit unhappy which is why he is sending out a warning noise.
Rabbits live so much happier in pairs though than on their own. Good luck with finding a match, there are so many rabbits in rescue because people breed them even by accident so hope you are able to give one of those a home.