3 months in Thailand/Indonesia - how many swimsuits?

Hey all, I’m studying abroad for three months this fall (September-November) and will spend one month each in Chiang Mai, Bali, and Koh Phangan.

How many swimsuits (bikini bottoms, tops, or one pieces) should I (23F) bring for those three months? I’m from somewhere very cold, so I’m not used to dealing with this type of climate at all.

I like packing light and will try to limit myself to one carry-on suitcase, plus a small duffle bag.