My wife and I will be returning to Thailand arriving Phuket(for Khao Lak) from Kuala Lumpur on 26th November 2010, departing Phuket to KL on 15th April 2011. On 2nd March we will be going to Australia from Phuket via Kuala Lumpur, returning 16th March to Phuket again via KL.

We had intended like last year to get a Non-Immigrant Type O multiple entry visa, which would give us 90 days from entry meaning a visa run or extension before 26th February. Am I right that we can go to Phang Nga immigration and get a 7 day extension for 1900 baht each which will cover us until our return from Australia when we will get a further 90 days, or do a visa run up to Ranong which will give us a further 90 days on re-entry from Myanmar?

Are there any other options for this scenario?

If you have multi entry O visas both those options should be available. You could also do the border run early when it was convenient for you.