I think EU should do the same like Canada. Thais who have had a Schengen visa in last 10 years should be able to use ETIAS.
If I’m not mistaken Thai citizens who have had US or Canada’s visitor visa in last 10 years are able to use just ETA for their travels to Canada.
I think EU (Schengen) and UK should introduce same system for Thais what Canada already have. If Thai Citizen who owns biometric passport have had Schengen/UK Visitor visa in last 10 years then they should be available to apply for ETIAS or ETA for the UK.