Originally Posted by A_Lee

I'm a bit confused. Do you want business class, or do you want economy class but only business class is available for the times you want? At first I thought it was the latter, but after your last post think it must be the former. I have no problem finding earlier flights in either. If you want business class, there are two fares to select from, ฿9,370.00 and ฿9,550.00. ฿9,370.00 is for only Thai Smile flights, but if you select ฿9,550.00, then all flights are available, but in selecting certain outbound flights will limit your inbound flights in some cases to restrict the Thai Smile flight(s). But if you're looking at business class, you should probably be avoiding the Thai Smile flights anyways as it's very poor value for the money.

So I think in your case you're simply not selecting the right fare. Out of the six possible fares to select, you need to select the bottom right one (฿9,550.00) and you'll have almost the full range to choose from.