Thailand had a terrible start to the vaccine rollout initially.
"The outbreaks has highlighted criticisms of the country's vaccine programme for an over-reliance on AstraZeneca shots produced by royal-owned Siam Bioscience, a slow roll-out and a confusing registration system"
https://www.reuters.com/world/asia-pacific/thailand-starts-long-awaited-covid-19-vaccination-drive-2021-06-07/
Luckily the US donated 1,000,000 Pfeizer vaccine's to help alleviate the dearth of vaccines available.
Perhaps you were in the right place at the right time. I live in the Northeast and had to travel to Bangkok to get Pfeizer and Moderna boosters.
Anutin's plan was to aquire vaccines later as he thought they would be cheaper. They weren't and vaccines were difficult to aquire with long waiting lists.
"When the coronavirus threatened to spread across Thailand a year ago, Public Health Minister Anutin Charnvirakul shocked the country's doctors by scoffing at warnings and describing the deadly COVID-19 as "a common cold."
https://asia.nikkei.com/Politics/Turbulent-Thailand/Thailand-s-vaccine-failures-anger-Prayuth-s-business-support-base