Internal flight booking, now or on arrival

Hi all you twigs on the branches.

Can someone tell me what option would be the best. I have booked my long haul flights and will be arriving in BBK 18th Feb (Chinese new year) 19th I fly to Chiang Mai and 3 days later back to BBK then to Phuket. Whould it be best to book the internal flights now or wait till I want to leave and just go to the airport and see whats leaving town. :0) Thanks for any advice.

it will be cheaper to book in advance. money will be saved

Thanks Mary. Nok air here I come!

Air Asia had seriously cheap fares for those dates. Not sure if it's too close now, but last week I picked up some tickets for 338 baht + tax = just under 1000 baht.

Thanks as always Chanchao. will look now !