My experience today at Phayathai 2 hospital.
I'm 57 and have had 1 X Sinovac 4 weeks ago (registered while thaiintervac site was working)
I arrived very early for my appointment and was taken straight away, I was the only non Chinese. The staff didn't miss a beat switching from announcements in Mandarin to English when my turn came.
I was offered Sinovac or AZ - I took Sinovac for various reasons - the whole procedure lasted around 45 minutes including the 30 minute wait time. Very slick and professional staff, they are a credit to their profession.