What's the most time efficient way but while still being on a budget to get from Kuala Lumpur to Bangkok?

Our goal is to get from Bangkok to Krabi then to Ko Tao. Unless there's another beach that would be reccomended? We're on a 5 day time schedule. We were thinking 3 days invested into the beaches and then catch a flight north to chiang mai for 2 days & then back to Kuala Lumpur. If it's something that can be done w/o too much of a headache. Any advice would help out, thanks!