Thai Airways Domestic Flights
 

Does Thai airways offer travel passes that allow multiple stops during a specified time for domestic travel versus booking all individual tickets?

Yes.

http://www.star-alliance.com/star_al..._thailand.html

Here is one that is Thai Air specificallly:
http://www.thaiairways.com/Promotion...azing_fare.htm

So to travel from BKK to Chiang Rai to BKK then to Krabi (no direct flight to Krabi from Chiang Rai) back to BKK would take 4 flight coupons or would CR to Krabi be considered one leg? Also Thai does not fly to Siem Reap need to use Bangkok Air correct?

CR to Krabi is two legs.

Bangkok Air is the only airline that flies non-stop between Bangkok and Siem Reap.

To book the domestic flights for the special promotion fares and coupons can this be done through web site or call Thai Airways directly? Thanks for all the help. Planning first trip to Thailand and there seem to be a lot of inside info to know.

You may want to look at Bangkok Air's Discovery Pass if you're going to Siem Reap.

The promotion at thaiairways.com talks about trips: one-way trip, round-trip, circle-trip, a single open-jaw trip. I would be very surprised to find out that Chiang Rai to Krabi was anything other than one trip.