Joshua won a great victory in chapter 10 and the sun stood still. Other kings decided to join forces to fight against Joshua in Chapter 11 including the king of Shimron:
1 When Jabin king of Hazor heard of this, he sent word to Jobab king of Madon, to the kings of Shimron and Akshaph,
They were also defeated as listed in Joshua 12:
the king of Shimron Meron one the king of Akshaph one
Yes, king of Shimron was the same one as king of Shimron Meron. Joshua even kept the order of the two names: Shimron, then Akahaph.
Cambridge Bible for Schools and Colleges mentions that Shimron Meron is the full name.
Before Joshua retired, he allotted the territory of Shimron to Zebulun in Joshua 19:
10 The third lot came up for Zebulun according to its clans: ...
15 Included were Kattath, Nahalal, Shimron, Idalah and Bethlehem. There were twelve towns and their villages.
Everything is quite consistent if we treat the two names pointing to the same place.