Trips from Singapore?

A friend and I are traveling to Singapore in late May. We have roughly a week to spend, and we're planning on spending 2 nights in Singapore, visiting somewhere else, and then returning to Singapore the night before our flight. That gives us ~5 days to fill in, and we're looking for options in Malaysia, Thailand, or Bali. I'm aware 5 days is a short time frame, but we don't mind being rushed. We're mostly interested in trying new food and exploring nature, but open to anything. I'm mainly concerned about the weather in those regions in late May, as I've heard it is monsoon season.

I would really appreciate any suggestions on where we should visit, or other advice you might have, thank you!