You can start booking your accommodation from the 4th of December when the dates become available. The earlier book the better rate you should get - If booking direct you do not need to pay until you get there so if a cheaper room becomes available throughout the year you can swap around.
We use the Wise cards or just our Credit card. Setting yourself up on wise is free and comes with a free card - you can convert the your currency to multiples currencies. Website - https://wise.com/
We are hoping to leave Wednesday the 19th of November getting into Kota Kinabalu Thursday the 20th - But completely up to you on when you wish to join us :) We should still be there till Thursday the 27th of November.