Junta chief Gen Prayuth Chan-ocha presided over the commission that met to choose the position as acting Police Chief Watcharapol Prasarnrajkit is retiring this September.
Other candidates for the top police post included Deputy Police Chief Gen Aek Angsananont.
However a source said Watcharapol nominated Somyot as the sole candidate and the commission agreed unamimously for Somyot to be successor of Watcharapol.
Earlier critics said Somyot would win over Aek as the new police chief graduated from the Royal Police Cadet Academy while Aek began his police career with a bachelor's degree in law from Ramkamhaeng University.
Both Aek and Somyot oversee crime suppression and internal security, and they have both made a name for themselves cracking high-profile criminal and political cases as well as the suppression of narcotics and auto theft.