All appointments for Moderna jabs were snapped up just seconds after registration opened at Phyathai 2 Hospital in Bangkok on Thursday
Each customer was permitted to reserve up to two doses of the alternative vaccine at 1,650 baht per dose.
They were required to pay the full amount up front in exchange for an e-coupon. The booking cannot be cancelled or refunded, but can be transferred to another recipient, said the hospital.
The Moderna jab is an alternative to the Sinovac and AstraZeneca jabs directly procured by the government for its free vaccination rollout.
Disappointed customers complained they had registered for the Moderna shot at 12.01pm only to find that registration was closed because appointments had all been snapped up.
The hospital explained that its whole vaccine quota allotted by the Government Pharmaceutical Organisation had been booked up, though it did not reveal how many jabs it had been given.
Bangkok recorded 2,212 new cases of Covid-19 on Thursday as the country registered a daily record of 7,058 infections and 75 deaths.