Cannabis is so readily available in the UK it is unlikely that anyone is going to rush over to Thailand because it is now legalised. Thailand has long been a country of choice for backpackers as drugs and cheap booze are, and always have been, readily available. This goes right back to the sixties. My first trip, (excuse the pun) was actually in 1969 as a continuation of my odyssey to India.
And that brings me on to another point about cannabis in general. Just about everyone I know have smoked it at some point. Many have enjoyed the odd joint over the years and still do. Smoking cannabis isn't just about kids today, most of the people I know who still enjoy it are drawing their pensions these days.