An umbrella, especially in rainy season.

A towel or sarong for drying after bathing.

Women should bring a sarong or similar to wear in the hot springs.

Men should bring shorts (swimming shorts, boxers) to wear in the hot springs.

Mosquito repellent (not coils).

Loose clothing that cannot be seen through and covers from shoulders down to knees.

Personal toiletries.

Your passport to deposit at registration.

Cash to pay for the retreat and for transport afterwards.

Shoes that are easy to take off, eg: sandals or flip-flops.

Torch (flashlight).

Women do need to wear bras.

Candles can be nice in rooms, as can incense.