I once did an online booking and for some reason there was a problem (though I can't recall now the exact details of what the problem was). I ended up calling TG in Thailand and they were able to take down my information and manually process the booking there as if it had been all done electronically. Try what others suggest but if you have a problem, such as the fare no longer being available, call to TG in Thailand and explain the problem.

Definitely double check that, but most definitely there are discount booking classes available in some markets to some destinations that do earn miles. The non-mileage earning booking classes are only economy and only V,W,G. Depending on which route you're flying, Q is very often one of the options. If you get an option to select which type of fare you want, first click on the link for each fare type and see if it says it earns miles or not, before selecting which one you want. Of course any business or first class tickets purchased will earn miles as there are no non-earning classes there for purchased tickets.