The cool season, roughly November to February, is the easiest time to be outdoors and the most comfortable fishing of the year. Mornings are pleasant, the middle of the day is bearable, and the lakes are busy with visitors for exactly that reason.
The hot season, March to May, is punishing from mid morning onwards and excellent at dawn. Fish feed early, then everything shuts down until late afternoon. Plan a five o'clock start and a long lunch and it is a productive time.
The wet season, roughly June to October, is the one people avoid and it is better than its reputation. Rain arrives in heavy bursts rather than all day, the temperature drops, and fish often feed hard immediately afterwards. Lakes are quieter and prices soften.
The genuine problem in the wet months is not rain but flooding at some of the outdoor venues, and access roads to the jungle lakes that turn to mud. Ring ahead rather than driving two hours on faith.
If you can only come once and want comfort, come in January. If you want the lake to yourself, come in September and accept getting wet.