Biking Southern Thailand Islands

Hi I've done quite a bit of research on which bike route I want to take
in Thailand now. I've decided to take the train from Bangkok to Chumpon first and then bike from there
down the west side of the coast to Krabi and Trang Island area. I was wondering if anyone has done that in the month
of February? Will have trouble finding places to stay as I go? We'll be biking for a month. We're in our 60's and are looking for
mid-range beach hotels and the odd upper-range hotel when we feel like splurging.
Should I book some places ahead of time, or will I have no trouble finding places to stay.
Thanks for any advice!
Sandy