Since the rest of the world starts giving third booster shots, will Thailand miss this development again or are booster shots ordered?

I have read that boosters are indeed being planned for. For 2 SinoVac jabs a 3rd booster of AZ already being distributed. For 2 AZ shots the plan is 6 months after 2nd shot to schedule booster...not sure what brand will be used.

Currently they are giving boosters to people who got 2*Sinovac or Sinopharm.

The next ones will probably be people who got Sinovac + AZ.

We've been informed, from different government sources (PM, DPM, MoH), that variously 60, or 65 or 120 mm doses are on order for 2022. Mostly AZ and Pfizer.

 

There have been many, many, many combinations, intervals and booster "strategies" which have been announced. Every possible combination has been "advocated".