I recieved the same message and when I asked the reason for the delay they replied with.
"In order to the pandemic of Covid-19 Delta varient in USA. The US government become reserving the vaccine for US citizen. This is a reason of vaccine for Thailand is postponed. The Private Hospital Association must pay the cost of vaccine to Moderna USA to ensure there are vaccines reserved for Thailand.
As an update, there is only 1.5 million doses of vaccine deliver to Thailand this year, which we do not expect to get this batch of the vaccine. "