Lawrence Okai volunteered for service in the Gold Coast Regiment of the Royal West African Frontier Force.
He was selected to be trained as officer at the Royal Military Academy Sandhurst (RMAS), in the United Kingdom and was commissioned on 16 December 1955.
General Okai was then chosen to be overall commander of the Armed Forces of Ghana, and was further promoted on appointment: he was Chief of the Defence Staff from December 1974 to November 1976.
The SMC was composed of the service chiefs and as the head of the armed forces, General Okai became a member of the military government.
He served in the junta until he retired as Chief of the Defence Staff in November 1976, when he was succeeded in both roles by Lieutenant General Fred Akuffo.