Daniel Ludlow suggests that the name of king Laman was a throne name:
Evidently the Lamanites have used the same procedure as the Nephites did in their early history of naming their kings after their earliest leader. Jacob 1:11 mentions that the kings who succeeded Nephi were known as "second Nephi, third Nephi, and so forth, according to the reigns of the kings." Thus it should not be too surprising to discover that the king of the Lamanites in approximately 178 B.C. was still known as "king Laman" (Mosiah 10:56), although the original leader after whom the king was named lived some four hundred years before. Also, later in the Book of Mormon we discover that the son who succeeded this king is also known as Laman." (see Mosiah 24:3). [Daniel H. Ludlow, A Companion to Your Study of the Book of Mormon, p. 181]
Note* Brant Gardner comments, however, that "it is not clear that this is a throne name as opposed to a personal name. . . . Nevertheless, what the name clearly is not, is King Nephi. The city of Nephi clearly came under some kind of Lamanite influence, and one way or the other, the connections to the Nephite leadership line had been lost. It is reasonable to assume that had the people of the city of Nephi continued their political allegiance to the lineage of Nephi, the name Laman would not have been a very popular one for the king. [Brant Gardner, "Book of Mormon Commentary," [http://www.highfiber.com/~nahualli/LDStopics/] Mosiah/Mosiah9.htm, pp.13-14]
Note* It is also very plausible that the name "Laman" is a metonymic name inserted by Mormon to imply that the Nephites left behind in the land of Nephi had assimilated the Lamanite cultural and religious ideas. [Alan C. Miner, Personal Notes]