I’m in a similar boat here in the south of Thailand. Especially during monsoon season. One day the RH will be in the 90s and other days it’s 50%.
I’m just starting to get into growing and I decided that the best way was to do it is inside.
Air conditioning can suck some of the moisture out of the air and keep the temps below 30C which is actually not even the hottest it gets outdoors (sometimes 32- 34C).
Sorry, I haven’t grown anything yet so difficult to give any recommendations but after burning up a few plants in seedling stage I just broke down and bought a small (3x3) grow tent and some lights.
Now all I have to worry about is keeping the room cool enough.