Tiger Airways' flys from Krabi to Singapore may also be a convenient connecting airport, especially if travelling from down under.

Tiger Airways' is a budget airline, so prices vary considerably.

-from Singapore: 6 flights weekly:
Mon, Wed, Fri, Sun at 16.10;
Tue and Thu at 07.40
priced as low as 500baht!

- to Singapore: 6 flights weekly:
Mon, Wed, Fri, Sun at 17.25;
Tue and Thu at 08.55

http://www.tigerairways.com/flight/flight-schedules-winter06.php

Singapore - Krabi
Flight Number	Departure Airport	Departure Time	Arrival Airport	Arrival Time	Frequency	Travel from	Travel to
TR188	SIN	1655	KBV	1735		29 Oct 06	24 Mar 07
TR189	KBV	1805	SIN	2050		29 Oct 06	24 Mar 07