Ive been living in Thailand on and off for almost 10 years. I started my journey in Chiang Mai, headed towards the Southern part of Thailand (Rayong, Hat Yai, etc) and spent a few years in BK. Ive never paid much attention to Wai's until the past two years living in the Northeast region. Prior to this, I just give my usual Wais to people close to my age range or older without much care. When it was given Id return it. Whenever I was with my mates they did so as well.
Im not sure if its a regional thing but Ive noticed a drop off being in the Northeast. No biggie. About a week ago a few of the local beauty pageant contestants when to dine where we were for a photo opp. It was my wife, myself and my mate. One of the contestants gave the Wai to my wife while I was eating. According to my mate, he gave one to her a second after my wife and claimed that he didnt get a return Wai back. He was a bit upset and I told him to chill since the beauty contestants looked nervous and it wasnt there focus. Also I told him sometimes people give Wais to a group than individual.
He then scolded me and told me it was rude since he was an older man, bla bla bla. I came here to the forums here to make it clear on this issue.
The only thing I notice is that in other regions in Thailand it was quite common whereas in BK and the Northeast it was the least. Also I tend to break the rules, like if a waiter or a maid Wai's at me Ill return it back.
