You can get the Covid extension on the STV which gives you 2 months each time. I’ve been to Phuket immigration and they confirmed it for my girlfriend.
Arrive on whatever visa you can and then switch to a
*****
month volunteer visa. I’m also not over 50- this was the best option I found and also have a 1 year old who just follows me on the visa. Speak with TMT travel who give a great service.