There are over 800 Isuzu buses serving Bangkok. These are the dominant models that can be easily found on the streets of the city:

Non-A/C Red bues: Isuzu MT111QB, there are 540 of these buses serving zone 1, 6, 7 and 8

A/C Blue buses: Isuzu CQA650 A/T, there are 100 of these buses serving zone 7

A/C Orange buses: Isuzu LV223S, there are 200 of these buses serving zone 1, 7 and 8