Bangkok, Ko Tao, Ko Phangan and Ko Samui: what order?

The cheapest sensible order is Bangkok → Ko Tao → Ko Phangan → Ko Samui — €40 of transport and 0.8 days spent moving.

Bangkok → Ko Tao → Ko Phangan → Ko Samui

• Bangkok → Ko Tao Bus + ferry · overnight 12h €25
• Ko Tao → Ko Phangan Ferry 1h €10
• Ko Phangan → Ko Samui Ferry 1h €5

You fly into BKK and home from USM — an open-jaw ticket, usually cheaper than doubling back.