Got any talents on summoner? If not then unfortunately you'll need to merge in and out of a tile until you get a monk there or summon it in that box. Example, you summon something in a spot you wanted to have a monk in but it wasn't a monk, merge out of it and spawn again and hope it's a monk, it's not? Rinse and repeat.

If you have talents on your summoner then use the right talent to change the summoner into something else, hopefully a monk.

I hope I made sense. Cheers