Chemoiywo began to enter the elite senior ranks of distance running in the early 1990s: he ran a best of 13:18.95 minutes for the 5000 metres in 1992, which placed him near the top 30 for the discipline that year.

[5][6] He established himself among the top international runners with a win over 5000 m in Durban at the 1993 African Championships in Athletics, beating Haile Gebrselassie who went on to become world champion later that year.

[7][8] He returned to the roads in South America at the end of the year, retaining his title at the Saint Silvester race and also winning at the Corrida San Fernando 10K.

[13] Turning to the track, he ran a 10,000 metres best of 27:25.82 minutes to win at the Sea Ray Relays and rank in the top ten for the discipline that season.

[14] Another personal best came at the Grande Premio Brasil Caixa de Atletismo, where he won the 3000 metres in a meet record of 7:43.15 minutes.

He was the worst performing of the Kenyan 5000 m team as he failed to progress beyond the heats while Ismael Kirui won the title and Shem Kororia took bronze.

He failed to defend his title by the smallest of margins, losing to fellow Kenyan Paul Koech with both registering the same time of 13:35.13 minutes.