From the 1st August 2008 until 31st January 2009 there is free travel on selected non air conditioned BMTA buses and on 164 3rd class SRT commuter and long distance trains.
The details of SRT’s free travel arrangements:
Free travel applies to all rural 3rd class commuter trains. Noted by a train number of 4xx on the timetables. Note: these do not operate into Bangkok.
Free travel applies to all Bangkok commuter trains. Noted by a train number of 3xx on the timetables. Note: These operate mostly at peak times.
Free travel applies to selected intercity 3rd class trains to and from Bangkok. These are Ordinary and some rapid trains marked as 1xx and 2xx on the timetables. The free travel is only valid up to the following stations Chumphon (Main south), Denchai (Main north), Nakhon Ratchasima (korat) and Khon Kaen (North East lines).
Free travel also applies to all Eastern line trains to and from Bangkok except air conditioned express DMUs. Also all Mahachai and Maeklong commuter trains are free.
If you want to see up country Thailand very cheaply and have the time I recommend taking these free trains. But I do advise getting to the station an hour before the train departs to get a seat. All the free trains are non aircon and will be very crowded. This is to be expected with anything that is free in Thailand. Everyone wants to use it. Mid week trains should be less crowded than Friday and weekend trains.
The details of BMTA’s Free travel arrangements.
Also from the 1st of August 2008 there is free travel on 72 BMTA operated bus routes. The free travel only applies to non air conditioned metro buses. These are the Red or White with green strip buses directly owned by the BMTA and not the private white and blue non air conditioned buses.
Not every non aircon bus operated by BMTA is free. All buses that are free will have a white and blue Thai language sign displayed at the front and back of the bus. Using these free buses will save you between 14 and 16 baht per day. But they are very popular and thus very crowded even close to the outer end of the routes. So getting a seat will be hard and even getting in the door maybe hard at peak times.
[ Edit: Sorry, no promos please. ]